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Developing a modern periodic table: From spirals to the stars

Published: 22 February 2019

The periodic table is one of the most iconic images in science, a guide to the chemistry of our world. But it's only one among many visual ways to classify the elements.

There are thousands of alternative periodic tables or systems, some predating the invention of the now-standard version you might know from the school chemistry lab.   

The earliest attempts to classify elements

The earliest attempts to classify matter, from metals to minerals, were based on the idea of essential qualities, or elements. Ancient Greek philosophers had four: air (hot and wet), water (cold and wet), earth (cold and dry) and fire (dry and hot). 

Grouping chemical substances together according to similar qualities had practical value for alchemists and apothecaries, but there was no consensus or underlying order.

Things began to change at the end of the 18th century, as chemists introduced classification based on measurable quantities, like weight. 

In 1789 one leading moderniser, the famed French chemist Antoine Lavoisier , produced a list of 33 ‘simple substances’ that made up the 300 or so chemicals known at the time, categorised by gases, metals, non-metals and earths.    

John Dalton , a Manchester schoolteacher, introduced the idea of classifying elements by the relative weight of their atoms  in 1806—a revolutionary concept at the time, which would be crucial to the invention of periodic tables. 

Today we know of 118 elements that can be combined to form over 70 million different chemical compounds, so having a system to classify these at an elemental level is crucial.

What is a periodic table?

'Periodic' tables are named as such because they order elements in such a way that their chemical properties repeat periodically. after regular intervals.

The figure most closely associated with the periodic table is Dmitri Mendeleev , the Russian chemist who devised his first table in 1869.

It looks unlike the modern form we know today, as the elements are arranged by ascending weight downwards, rather than across. 

But Mendeleev’s periodic table was not the first. There were five others before him. 

The idea had been in the air since the first international conference of chemistry in 1860 at Karlsruhe, Germany. At this meeting, standard values for the atomic weights of the 60 elements then known had been agreed by the world's leading chemists.

Yet the first periodic pioneer was not a chemist. 

Periodic pioneers

Dmitri Mendeleev, seen here around 1905, devised his first periodic table in 1869. 

Mendeleev's first table, published in the journal of the newly-formed Russian Chemical Society, looks unlike the modern form we know today.

In 1864 John Newlands classified the known elements into eight groups, which became known as the Law of Octaves.

Julius Lothar Meyer published an early version of the periodic table in 1864 which contained 28 elements.

What did the first periodic table look like?

In 1862 the French geologist Alexandre-Émile Béguyer de Chancourtois published a paper describing a classification of the elements. 

De Chancourtois' 'telluric screw', as he called it, placed the elements in order of atomic weight in a spiral pattern around a cylinder. 

De Chancourtois' periodic system. 

Like Mendeleev’s table, but seven years before, de Chancourtois had stumbled upon a periodic repetition of chemical properties in his arrangement. 

Unluckily for him, the groundbreaking paper escaped the attention of chemists for decades, largely because the publisher did not include a visual diagram of his screw system.   

In 1926 the Science Museum made a working model of de Chancourtois' periodic screw.

By turning the handle, you can see chemical groupings of elements, such as lithium, sodium and potassium (three of the alkali metals), align vertically down the rotating column.   

Atomic mass, weight or number?

• An element can come in different forms (isotopes), depending on how many neutrons it contains. Atomic weight is the average mass for an element across all its isotopes.
• Atomic mass is the mass of a particular atom or isotope. 
• An element's atomic number is the number of protons it has. Atomic number replaced atomic weight as the value that determines the order of the elements in the periodic table. 

Can periodic tables work in three dimensions?

The first periodic table—de Chancourtois’ screw—was not really a table at all, but a three-dimensional system for arranging the elements. 

The defining feature that unites de Chancourtois’ screw with Mendeleev’s table and many others is the periodic pattern of chemical properties, which allows chemists to predict how elements behave and react according to their position in the system. 

While it was Mendeleev’s two-dimensional table of rows and columns that became the standard form (confusingly, he always used the term ‘system’ over ‘table’), this did not discourage later chemists from introducing alternatives. 

As well as being visually attractive, some three-dimensional periodic systems contained extra information about the elements.  

See how de Chancourtois' system worked in practice:

What can alternative periodic systems tell us about the elements?

Perhaps the most important periodic system post-Mendeleev was a three-dimensional double spiral system by English scientist William Crookes  in 1888.

Crookes added the newly-discovered noble gases (helium, neon, argon, krypton, xenon, radon) to his system, which helped persuade Mendeleev that his table could be adapted to accommodate them.

But more interestingly, Crookes’ periodic system illustrated his theory of the evolution of the elements. In this, elements formed in a plasma (a hot state of matter) inside stars. As temperatures cooled, they evolved from the lightest element, hydrogen, at the top of his spiral, to the heaviest, uranium, at the bottom. 

Crookes' original model physically embodies one of the first evolutionary theories of the elements.

Is the famous periodic table the final one?

In the pursuit of the ultimate table, there were about 700 alternative versions published in the century after Mendeleev’s table of 1869.

Whatever their shape, from spirals and helices to zig-zags, circles and blobs, what unites them is the periodic law—that elements fall into repeating groups when ordered by their increasing atomic numbers.

This periodic table by the EU Chemical Society orders scales elements by their relative scarcity.

Alexander arrangement of the elements, devised by Roy Alexander in 1965.

Version of the periodic table by James Franklin Hyde, c.1975, with silicon at the centre.

The ADOMAH periodic table by Valery Tsimmerman (2006) is based on the earlier Janet table (1928).

But none of these has won the title of the definitive table.  

Even the famous version you might know provokes fierce debate among chemists about where certain groups or elements, like hydrogen, should be placed. And as new elements are added, it will continue to evolve.       

In recent decades, the Internet has opened up the practice of periodic table making to a wider public. As well as alternative forms, there are alternative contents: you can find periodic tables of almost anything, from wine to football.   

This proliferation of periodic tables not only reflects the ongoing scientific endeavour to classify the world around us.  

It also shows, as these tables have made the journey from textbook to tea mug design, how rooted science is in our cultural life.

Find out more about periodic tables

• Scerri, Eric R. ' The Periodic Table: A Very Short Introduction '. Oxford: OUP, 2011.
• Scerri, Eric R.  The Periodic Table: Its Story and Its Significance . Oxford: OUP, 2007.
• Mazurs, Edward G. Graphic Representations of the Periodic System during One Hundred Years. University of Alabama Press, 1974.
• Science Museum Blog, The periodic table in three dimensions
• Royal Society of Chemistry, Development of the periodic table
• Nature,  Celebrate the women behind the periodic table
• New Scientist, Up and atom: The fights to put people into the periodic table
• BBC Bitesize, The most weird and wonderful elements in the periodic table

Discover more

John Dalton—A new atomic theory

Discover the story of the Manchester-based scientist who formulated a new atomic theory to explain chemical reactions.

Playing with science: A brief history of the chemistry set

How have scientists and educators prepared children to be scientists over the centuries? Five objects in our collection hold some revealing clues.

Experimental Chemistry

Discover incredible objects associated with pioneering work in chemistry from the 18th century onwards.

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The periodic table of the elements

The periodic table is an arrangment of the chemical elements ordered by atomic number so that periodic properties of the elements (chemical periodicity) are made clear.

Explore the chemical elements through this periodic table

The standard form of the periodic table shown here includes periods (shown horizontally) and groups (shown vertically). The properties of elements in groups are similar in some respects to each other.

There is no one single or best structure for the periodic table but by whatever consensus there is, the form used here is very useful and the most common. The periodic table is a masterpiece of organised chemical information and the evolution of chemistry's periodic table into the current form is an astonishing achievement.

The International Union of Pure and Applied Chemistry (IUPAC) confirmed the names of elements 113, 115, 117, and 118 as:

• Nihonium (symbol Nh), for element 113
• Moscovium (symbol Mc), for element 115
• Tennessine (symbol Ts), for element 117
• Oganesson (symbol Og), for element 118

This followed a 5-month period of public review after which the names earlier proposed by the discoverers were approved by IUPAC.

On 1 May 2014 a paper published in Phys. Rev. Lett by J. Khuyagbaatar and others states the superheavy element with atomic number Z = 117 (ununseptium) was produced as an evaporation residue in the 48 Ca and 249 Bk fusion reaction at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. The radioactive decay of evaporation residues and their α-decay products was studied using a detection setup that allows measurement of decays of single atomic nuclei with very short half-lives. Two decay chains comprising seven α-decays and a spontaneous fission each were identified and assigned to the isotope 294 Uus (element 117) and its decay products.

Images of various periodic tables

Click on the images below to see images of the periodic table in a variety of styles.

May 14, 2024

14 min read

Superheavy Elements Are Breaking the Periodic Table

Extreme atoms are pushing the bounds of physics and chemistry

By Stephanie Pappas

Quarternative

A t the far end of the periodic table is a realm where nothing is quite as it should be. The elements here, starting at atomic number 104 (rutherfordium), have never been found in nature. In fact, they’d emphatically prefer not to exist. Their nuclei, bursting with protons and neutrons, tear themselves apart via fission or radioactive decay within instants of their creation.

These are the superheavy elements : after rutherfordium come dubnium, seaborgium, bohrium, and other oddities, all the way up to the heaviest element ever created, oganesson, element 118 . Humans have only ever made vanishingly small amounts of these elements. As of 2020 , 18 years after the first successful creation of oganesson in a laboratory, scientists had reported making a total of five atoms of it. Even if they could make much more, it would never be the kind of stuff you could hold in your hand—oganesson is so radioactive that it would be less matter, more heat.

Using ultrafast, atom-at-a-time methods, researchers are starting to explore this unmapped region of the periodic table and finding it as fantastical as any medieval cartographer’s imaginings. Here at the uncharted coastline of chemistry, atoms have a host of weird properties, from pumpkin-shaped nuclei to electrons bound so tightly to the nucleus they’re subject to the rules of relativity, not unlike objects orbiting a black hole.

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Their properties may reveal more about the primordial elements created in massive astrophysical phenomena such as supernovae and neutron star mergers. But more than that, studying this strange matter may help scientists understand the more typical matter that occurs naturally all around us. As researchers get better at pinning these atoms down and measuring them, they’re pushing the boundaries of the way we organize matter in the first place.

“The periodic table is something fundamental,” says Witold Nazarewicz, a theoretical nuclear physicist and chief scientist at the Facility for Rare Isotope Beams at Michigan State University. “What are the limits of this concept? What are the limits of atomic physics? Where is the end of chemistry ?”

Affixed to the wall in a concrete-block corridor known as Cave 1 in Lawrence Berkeley National Laboratory (LBNL), just steps from one of the few instruments in the world that can create superheavy atoms, is a poster-size printout of a table that organizes elements by nuclide, meaning based on the number of protons and neutrons in the nucleus. This graph shows all the known information about the nuclear structure and decay of the elements, as well as of their isotopes—variations on elements with the same number of protons in the nucleus but different numbers of neutrons.

It’s a living document. There’s a typo in the title, and there are tears along the poster’s edges where duct tape holds it to the wall. It’s been marked up with notations in Sharpie, added after the poster was printed in 2006. These notations are the atomic physics version of seafarers penciling in new islands as they sail, but in this case, the islands are isotopes of elements so heavy they can be seen only in particle accelerators like the one here. In a field where it can take a week to make just one atom of what you want, a record of progress is essential.

“Everybody likes the handwritten part,” says Jacklyn Gates, who leads LBNL’s Heavy Element Group. “If we were to print this out from 2023—”

“It’s not as fun,” chimes in Jennifer Pore, a staff scientist in the lab.

“It’s not as fun,” Gates agrees.

Gates is a nuclear chemist with a wry sense of humor and a clear fondness for the equipment that she and her team have developed to synthesize superheavy elements . They create these elements by smashing standard-size atoms together in a 2.2-meter-wide cyclotron—a drum-shaped particle accelerator—in a lab perched on a hillside above the city of Berkeley. Construction on the cyclotron started in 1958, after the fallout from the first nuclear bomb explosions began turning up in the form of new radioactive elements such as fermium (atomic number 100). Much of the original cyclotron persists today; in the control room, silver dials that wouldn’t be out of place in a cold war–era thriller sit beside beige panels from the 1980s and blue banks of buttons from modern updates.

The first of the superheavies, rutherfordium, was synthesized here in 1969. Rutherfordium, named after Ernest Rutherford, who helped to explain the structure of atoms, was also made a few years prior by the Russian Joint Institute for Nuclear Research (JINR) in Dubna, the same group that first created oganesson in 2002 (named after Yuri Oganessian, who led the team that created it). Beginning in the late 1950s, the competition to add new elements got hotter than the ion beams used to make them. Today the vicious disputes over who synthesized what first, mostly between the Berkeley lab and JINR, are remembered as the Transferium Wars.

By the 1980s Germany had joined the fray with its nuclear research institute, Gesellschaft für Schwerionenforschung (GSI), or the Society for Heavy Ion Research. The numbers ticked higher, with the three teams trading off naming rights up to copernicium (element 112, named after Nicolaus Copernicus), discovered in 1996. Controversy continued to dog the superheavies; in 1999 researchers at LBNL announced the discovery of element 116, now known as livermorium after Lawrence Livermore National Laboratory, only to retract that claim after finding that one of their scientists had fabricated evidence. (JINR successfully created livermorium in 2000.) In 2004 Japan’s Institute of Physical and Chemical Research (RIKEN) synthesized element 113, nihonium, after the Japanese word for “Japan.” Although element 118 is the heaviest element ever synthesized, the most recently discovered is actually 117 , tennessine, which was announced by JINR in 2010. The scientists behind the discovery named it in tribute to the state of Tennessee , home to several institutions that played a role in the experiments.

“What are the limits of atomic physics? Where is the end of chemistry?” —Witold Nazarewicz Michigan State University

The race to create ever heavier elements continues to this day, and not just because the researchers who succeed get to name a new element in the periodic table. It’s also because theorists predict that certain combinations of protons and neutrons may land in an “island of stability” where these elements will stop decaying immediately. “Some theories predict a year half-life, or 100 or 1,000 days,” says Hiromitsu Haba, a physicist and director of the Nuclear Chemistry Group at RIKEN, which is currently on the hunt for element 119.

A half-life—the time it takes for about half of a substance’s atoms to decay—that long would be enough for serious experimentation or even use in new technologies. For now, though, research into superheavies is focused on their fundamental properties and what they can reveal about nuclear dynamics, not what they can do as materials themselves. That doesn’t mean they won’t eventually become useful, however.

“Everything we’re doing right now ... it doesn’t have practical applications,” Gates says. “But if you look at your cell phone and all the technology that went into that—that technology started back in the Bronze Age. People didn’t know it would result in these devices that we’re all glued to and utterly dependent on. So can superheavy elements be useful? Maybe not in my generation but maybe a generation or two down the road, when we have better technology and can make these things a little bit easier.”

Making these elements is far from easy. Researchers do it by shooting a beam of heavy ions (in this case, large atomic nuclei without their electrons) at a target material in the hopes of overcoming the electrostatic repulsion between two positively charged nuclei and forcing them to fuse. At LBNL, the source of the ion beam is a device called VENUS (for “versatile electron cyclotron resonance ion source for nuclear science”), which sits at the top of the cyclotron behind fencing festooned with radiation warnings. Within VENUS, a combination of microwaves and strong magnetic fields strips electrons off a chosen element (often calcium or argon in Gates’s experiments). The resulting ions shoot down a pipeline into the cyclotron, which sweeps the ions around in a spiral, accelerating the beam.

Technicians in the control room use electrostatic forces to direct the beam out of the cyclotron and into instruments in the “caves,” low corridors that come off the cyclotron like spokes. The caves contain beam targets; the one in Cave 1 is a thin metal foil about the diameter of a salad plate. The targets rotate so the beam doesn’t hit any single spot for too long. They can melt when bombarded with speeding ions, Gates says.

What the target is made of depends on how many protons the researchers want in the final product. For example, to make flerovium (114 protons, named after Russian physicist Georgy Flerov, who founded JINR), they need to hit plutonium (94 protons) with calcium (20 protons). To make element 118, oganesson, scientists beam calcium at californium (98 protons). The more neutrons they can pack into the ion beam, the more they can ultimately cram into the final product, making even heavier isotopes.

Most of the time the beam passes right through the target without any nuclear interactions. But with six trillion beam particles winging through the targets per second, an eventual nucleus-to-nucleus collision is inevitable. When conditions are just right, these pileups mash the nuclei together, creating a very temporary new superheavy atom moving at nearly 600,000 meters per second.

Jen Christiansen

To slow down these speeding heavyweights, the researchers use helium gas and electric fields to guide the particles into a trap for measurement. They can also pump in other gases to see what kinds of chemical reactions a superheavy element will undergo before it decays. But that’s feasible only if the element lasts long enough, says Christoph E. Düllmann, head of the superheavy element chemistry research group at GSI. To conduct and study chemical reactions, researchers require an element with a half-life of at least half a second.

Scientists quantify superheavy elements and their reaction products by measuring the energy they give off during alpha decay, the shedding of bundles of two protons and two neutrons. In a room called the Shack at LBNL, researchers wait on tenterhooks for data points showing them where these alpha-decay particles land inside the detector; their journey reveals information about the composition of the original atoms and any reactions they’ve undergone. It’s hard to imagine that chemistry physically happening, Pore says: “It almost feels like it exists somewhere else.”

T he heaviest element that researchers have studied chemically is flerovium (114)—the heaviest one that can be created in the quantities and with the duration needed for chemical experiments. Scientists can produce flerovium at a rate of about three atoms a day, Düllmann says. “A typical experiment needs about one month of total run time,” he says. “Not every atom that is produced will reach your chemistry setup, and not every atom that reaches your chemistry setup will be detected in the end.”

A few atoms can reveal a lot, however. Before flerovium was synthesized, some theories predicted that it might act like a noble gas—inert and nonreactive—and others suggested it might act like a metal, specifically, mercury. Experiments on the element published in 2022 in the journal Frontiers in Chemistry showed something weirder. At room temperature, flerovium forms a strong bond with gold, very unlike a noble gas. It also bonds with gold at liquid-nitrogen temperatures (–196 degrees Celsius). Oddly, though, at temperatures between these two, the element doesn’t react.

Oganesson is grouped in the periodic table with the noble gases, but researchers think it is neither noble nor a gas. It’s probably a solid at room temperature, according to research published in 2020 in Angewandte Chemie , and transitions to liquid around 52 degrees C. There are many such examples, says Peter Schwerdtfeger, a theoretical chemist at Massey University in New Zealand and senior author of the 2020 paper.

The reason for these strange characteristics has to do with the electrons. Electrons orbit nuclei at certain energy levels known as shells, each of which can hold a specific number of electrons. Electrons in outer shells—where there may not be enough electrons to completely fill the shell—are responsible for forging chemical bonds with other atoms. Each shell ostensibly represents a specific distance from the nucleus, although the actual path of an electron’s orbit in that shell (called an orbital) is often far from a simple circle and can look more like a dumbbell, doughnut, teardrop, or other configuration. (According to quantum mechanics, these outlines merely represent the places where an electron is likely to be found if pinned down by an actual measurement. Otherwise, electrons mostly exist in a haze of probability somewhere around the nucleus.)

As a nucleus gets heavier, electrons near it feel an extreme pull from the glut of positive charges there, drawing them in closer and reducing the space they have to move around in. Because of the uncertainty principle, which states that a particle’s position and speed can’t be known precisely at the same time, this reduction in the electrons’ elbow room means their velocity must increase via a kind of seesawing of fundamental physical laws. Soon the electrons are traveling at nearly the speed of light. As Einstein’s general theory of relativity suggests, objects moving this fast gain mass and get weird. In particular, the orbits of electrons in the lowest-energy states—the innermost shells—around a superheavy nucleus tend to contract, creating a greater density of electrons closer to the nucleus, Schwerdtfeger says. These changes are known as relativistic effects.

These effects show up even in naturally occurring elements of the periodic table. Gold is yellowish because relativistic effects shrink the gap between two of its electron shells, slightly shifting the wavelengths of light that the element absorbs and reflects. Yet relativistic effects don’t usually play a huge role in the chemical behavior of most light elements. That’s why the order of elements in the periodic table is based on the number of protons in each element’s nucleus. This arrangement serves to group together substances with similar chemical properties, which are determined mainly by the number of electrons in outer shells that are available for chemical bonds.

“The periodic table is supposed to tell you what the chemical trends are,” LBNL’s Pore says. For heavier elements, in which relativistic effects start to rule, that’s not necessarily true. In research published in 2018 in the journal Physical Review Letters , Schwerdtfeger and his colleagues found that because of relativistic effects, oganesson’s electron cloud looks like a big, fuzzy smear with no major distinction between the shells.

Even outside superheavy territory, chemists debate the placement of certain elements in the periodic table. Since 2015 a working group at the International Union of Pure and Applied Chemistry has been refereeing a debate over which elements should go in the third column of the table: lanthanum and actinium (elements 57 and 89) or lutetium and lawrencium (71 and 103). The debate centers on misbehaving electrons: because of relativistic effects, the outermost electrons orbiting these elements aren’t where they should be according to the periodic table. After nine years of official consideration, there is still no consensus on how to group these elements. Such problems only become more pressing at the heavier end of the table. “We’re trying to probe where that organization begins to break down and where the periodic table begins to stop being useful,” Gates says.

Along with a window into the limits of chemistry, the dance of electrons can provide a peek into the dynamics of the nucleus at the extremes. In a nucleus groaning with protons and neutrons, interactions between these particles often warp the shape into something other than the stereotypical sphere you’ll see in diagrams of atoms. Most of the superheavy elements that have been probed so far have oblong nuclei shaped like footballs, says Michael Block, a physicist at GSI. Theoretically, heavier ones that haven’t been synthesized yet might have nuclei shaped like flying saucers or even bubbles, with empty or low-density spots right in the center. Scientists “see” these shapes by measuring minuscule changes in electron orbits, which are affected by the arrangement of the positive charges in the nucleus. “This allows us to tell what the size of the nucleus is and what the shape of the nucleus is,” Block says.

The layout of the nucleus holds the key to whether anyone will ever be able to synthesize a superheavy element that sticks around. Certain numbers of protons and neutrons (collectively dubbed nucleons) are known as magic numbers because nuclei with these numbers can hold together particularly well. Like electrons, nucleons occupy shells, and these magic numbers represent the tallies needed to fill nucleonic shells completely. The island of stability that researchers hope to find in a yet undiscovered superheavy element or isotope would be the result of “double magic”—theoretically ideal numbers of both protons and neutrons.

Whether such a thing exists is an open question because heavy nuclei might tear themselves apart rather than tolerating the required numbers of nucleons. “Fission is the killer,” M.S.U.’s Nazarewicz observes.

Unlike the (relatively) gradual whittling down of a nucleus by alpha decay, nuclear fission is a sudden and utter dissolution. Different models yield different predictions about how many particles can be packed into a nucleus before fission becomes inevitable, Nazarewicz says. Theorists are trying to determine this limit to understand how large nuclei can truly get.

There is an interesting liminal space at the edges of what nuclei can bear, Nazarewicz notes. To be declared an element, a nucleus must survive for at least 10 –14 second, the time it takes for electrons to glom on and form an atom. But in theory, nuclear lifetimes can be as short as 10 –21 second. In this infinitesimal gap, you might find nuclei without electron clouds, incapable of chemistry, he says.

“The periodic table breaks with the heaviest elements already,” Nazarewicz says. The question is, Where do you break chemistry altogether? Anoth­er way to understand superheavy elements is to look for them in space. The elements heavier than iron (atomic number 26) form in nature through a process called rapid neutron capture, which often occurs in cataclysmic events such as a collision of two neutron stars.

Jen Christiansen; Source: National Center for Biotechnology Information; https://pubchem.ncbi.nlm.nih.gov/periodic-table/ ( reference )

If superheavies have ever arisen naturally in the universe, they were made by this process, too, says Gabriel Mar­tín­ez-­Pinedo, an astrophysicist at GSI. In rapid neutron ­capture, also known as the r-process, a seed nucleus grabs free nearby neutrons, quickly taking on the mass to make heavy isotopes. This must happen in an environment with ample neutrons roaming freely, which is why neutron star mergers are opportune spots.

In 2017 scientists observed a neutron star merger for the first time by detecting gravitational waves created by the interaction. “That was the very first confirmation that, indeed, the r-process happens during the merger of two neutron stars,” Martínez-Pinedo says. Researchers detected isotopes of lanthanide elements (atomic numbers 57 to 71) in that merger but, as they reported in Nature at the time, couldn’t narrow down the exact elements present. Detecting any superheavy elements will be even trickier because researchers will need to know which unique wavelengths of light those elements emit and absorb and pick them out of what Martínez-Pinedo calls the “complicated soup of elements” that emerges from one of these events.

In December 2023, however, astronomers re­­ported in the journal Science that there are excess amounts of several lighter elements—ruthenium, rhodium, palladium and silver—in some stars. These elements may be overrepresented because they are the result of heavy or superheavy elements breaking apart via fission. The findings hint that nuclei with as many as 260 protons and neutrons might form via the r-process.

Even if superheavy elements created in neutron star mergers were to decay away quickly, knowing they existed would help scientists write a history of matter in the universe, Martínez-Pinedo says. New observatories such as the James Webb Space Telescope and the upcoming Vera C. Rubin Observatory in Chile should make it possible to see other cosmic events capable of creating superheavy elements. “And there will be new gravitational-wave detectors that will allow us to see much larger distances and with higher precision,” he adds.

At the Facility for Rare Isotope Beams in Michigan, a new high-energy beam promises to give further insights into the r-process by packing more neutrons into isotopes than ever before possible. These are not new superheavies but beefed-up versions of lighter elements. In February researchers reported in the journal Physical Review Letters that they had created heavy isotopes of thulium, ytterbium and lutetium using just one 270th of their beams’ ultimate planned power output. At higher power levels they should be able to make the kinds of isotopes that eventually decay into heavier stable metals such as gold. “This may provide a pathway to some of the interesting isotopes for astrophysics,” says Brad Sherrill, a physicist at M.S.U. and a co-author of that study.

Meanwhile other scientists around the world are also looking to amp up their ion beams and targets to push past element 118. In addition, they’re increasing the precision with which they can capture and measure these elements. Researchers at the Facility for Rare Isotope Beams plan to improve their ability to differentiate between particles by a factor of 10. GSI will soon have a next-generation accelerator for superheavy synthesis. And at LBNL, Gates and her team are installing instruments to take higher-precision measurements of the mass of single atoms.

These new tools should further reveal the contours of chemistry at the extremes. “When we do superheavy chemistry,” Massey’s Schwerdtfeger says, “we see surprises all over the place.”

Stephanie Pappas is a freelance science journalist based in Denver, Colo.

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• Published: 11 December 2023

The quest for superheavy elements and the limit of the periodic table

• Odile R. Smits 1 ,
• Christoph E. Düllmann   ORCID: orcid.org/0000-0002-1194-0423 2 , 3 , 4 ,
• Paul Indelicato   ORCID: orcid.org/0000-0003-4668-8958 5 ,
• Witold Nazarewicz   ORCID: orcid.org/0000-0002-8084-7425 6 &
• Peter Schwerdtfeger 1  

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• Electronic structure of atoms and molecules
• Superheavy elements
• Theoretical nuclear physics

The borders of the periodic table of the elements and of the chart of nuclides are not set in stone. The desire to explore the properties of atoms and their nuclei in a regime of very large numbers of electrons, protons and neutrons has motivated new experimental facilities to create new elements and nuclides at the limits of atomic number and mass. But the small production rates and short lifetimes of superheavy nuclei and their atoms mean that ‘atom-at-a-time’ studies are the only experimental way to probe them. The physical and chemical data obtained so far, augmented by theoretical calculations, indicate significant deviations from extrapolations from lighter elements and isotopes. This situation raises the following question: how much further can one push the limits of the periodic table? In this Review, we describe the major challenges in the field of the superheavy elements and speculate about future directions.

Experiments to synthesize new superheavy nuclei and elements beyond the heaviest currently known element oganesson are underway. These systems will be crucial for benchmarking and testing many-body atomic and nuclear theory.

Rapid and efficient chemistry experiments with single atoms and molecules elucidate the influence of the high atomic charge on chemical properties, thus probing the fundamental architecture of the periodic table.

The field of superheavy element research puts atomic and nuclear theory to the test. For many superheavy systems, all available information must come from theoretical extrapolations based on models aided by high-performance computing and machine learning.

The presence of large electrostatic forces gives rise to pronounced relativistic effects in the atomic system and strong Coulomb frustration effects in the nuclear system. There are theoretical suggestions indicating that superheavy atoms should differ fundamentally from lighter species, leading to deviations from the current patterns of the periodic table.

Fundamental difficulties are encountered when dealing with the many-particle Dirac equation, as beyond a certain nuclear charge, levels such as the 1 s are predicted to merge with the negative-energy continuum, eventually leading to a potentially unstable atomic structure and real electron–positron pair creation.

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Acknowledgements

We thank V. Pershina, M. Block, J. Khuyagbaatar and W. Loveland for discussions. We acknowledge financial support by the Program Hubert Curien Dumont d’Urville New Zealand - France Science & Technology Support Program number 43245QC, and the Marsden Fund of the Royal Society of New Zealand. This work was also supported by the US Department of Energy under Award Numbers DOE-DE-NA0004074 (NNSA, the Stewardship Science Academic Alliances program) and DE-SC0013365 and DE-SC0023175 (Office of Science, Office of Nuclear Physics).

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Christoph E. Düllmann

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Chemistry studies in which only single atoms of the element of interest are present owing to small production rates and short half-lives.

Machine learning methods based on or applying Bayesian statistics.

The competition between the short-range attractive nuclear interaction and the long-range Coulomb repulsion leading to exotic topologies of nucleonic densities.

Density functional theory is an alternative to wave function-based methods using approximate functionals of the one-particle densities and currents.

The difference between an atomic or molecular property evaluated with a single determinant at the Dirac–Hartree–Fock level and the same evaluated using either a sum of determinants or many-body perturbation theory.

Nuclear reactions induced by ions with Z  > 2, with superheavy elements typically being produced in cold fusion reactions based on targets near 208 Pb that form a compound nucleus that is excited typically in the range of E CN  < 20 MeV and favourable for the production of the elements with Z  < 113, or in hot fusion reactions using 48 Ca beams leading to more highly excited (hotter) compound nuclei which evaporate more neutrons to de-excite, favourable for the production of the elements with Z  > 112.

Nuclear reactions in which beam nuclei and target nuclei exchange nucleons (in contrast to fusion reactions in which they fuse, forming a compound nucleus comprising all nucleons of beam nucleus and target nucleus).

The continuum spectrum with energy below − mc 2 that are a solution to the Dirac equation.

The boundary beyond which atomic nuclei are unbound with respect to the emission of a nucleon.

Relativistic quantum field theory of the interactions of charged particles with the quantized electromagnetic field (that is, photons) containing in particular contributions of particle vacuum fluctuations (virtual electron–positron pairs) leading to the vacuum polarization and the electromagnetic field fluctuations leading to the self-energy.

Ion beams consisting of radioactive ions.

A network of nuclear reactions taking place in high-neutron density environments that is responsible for the creation of approximately half of the atomic nuclei heavier than iron.

Electromagnetic separators isolating single superheavy nuclei from the intense primary ion beam and from unwanted byproducts of the nuclear formation reaction to allow their detailed study.

The difference between solutions of the nonrelativistic Schrödinger and the relativistic Dirac equation for a specific property.

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Smits, O.R., Düllmann, C.E., Indelicato, P. et al. The quest for superheavy elements and the limit of the periodic table. Nat Rev Phys 6 , 86–98 (2024). https://doi.org/10.1038/s42254-023-00668-y

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Periodic Table of Experiments

July 13, 2018 By Emma Vanstone 3 Comments

Just a quick post today for a bit of fun! What do you think of my Periodic Table of Experiments ?? It’s jam packed full of easy science experiments for kids !

You can download the periodic table as a clickable pdf. To see the activities you just need to click on the one you’re interested in!

There are a few that aren’t fully written up yet, but 90% of the links take you to fully written up ideas. Please bear with me on the rest!

Anyone fancy trying to do all of these over the summer holidays?

Click on the image to see a bigger version.

Download the clickable pdf periodic table here.

Just to clarify, this is not a real periodic table. You can see a real version with explanations for what each element is used for here .

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Last Updated on March 15, 2020 by Emma Vanstone

Safety Notice

Science Sparks ( Wild Sparks Enterprises Ltd ) are not liable for the actions of activity of any person who uses the information in this resource or in any of the suggested further resources. Science Sparks assume no liability with regard to injuries or damage to property that may occur as a result of using the information and carrying out the practical activities contained in this resource or in any of the suggested further resources.

These activities are designed to be carried out by children working with a parent, guardian or other appropriate adult. The adult involved is fully responsible for ensuring that the activities are carried out safely.

Reader Interactions

July 15, 2018 at 9:19 am

What a fantastic idea. I am working special needs adults and I will definitely use this from September onwards. Looking forward to this

July 16, 2018 at 8:21 am

I think this periodic table is great – however it would be helpful to have a list of what the experiments actually are – I haven’t done “trap the wolf” for example. Any chance of a link to each one?

July 16, 2018 at 3:20 pm

Love this! What category is the lavender (2nd from right) to be? I would love links to these activities!

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Printable Periodic Table PDF

Ptable's new, up-to-date periodic table PDF and wide periodic table PDF are layered so you can choose exactly what you want to print, and are the perfect companion to the periodic table classroom poster .

Just open the file in a PDF reader supporting layers and begin customizing!

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The periodic table is a tabular array of the chemical elements organized by atomic number , from the element with the lowest atomic number, hydrogen , to the element with the highest atomic number, oganesson . The atomic number of an element is the number of protons in the nucleus of an atom of that element. Hydrogen has 1 proton, and oganesson has 118.

What do periodic table groups have in common?

The groups of the periodic table are displayed as vertical columns numbered from 1 to 18. The elements in a group have very similar chemical properties, which arise from the number of valence electrons present—that is, the number of electrons in the outermost shell of an atom .

The arrangement of the elements in the periodic table comes from the electronic configuration of the elements. Because of the Pauli exclusion principle , no more than two electrons can fill the same orbital. The first row of the periodic table consists of just two elements, hydrogen and helium . As atoms have more electrons, they have more orbits available to fill, and thus the rows contain more elements farther down in the table.

The periodic table has two rows at the bottom that are usually split out from the main body of the table. These rows contain elements in the lanthanoid and actinoid series, usually from 57 to 71 ( lanthanum to lutetium ) and 89 to 103 ( actinium to lawrencium ), respectively. There is no scientific reason for this. It is merely done to make the table more compact.

periodic table , in chemistry , the organized array of all the chemical elements in order of increasing atomic number —i.e., the total number of protons in the atomic nucleus. When the chemical elements are thus arranged, there is a recurring pattern called the “periodic law” in their properties, in which elements in the same column (group) have similar properties. The initial discovery, which was made by Dmitry I. Mendeleev in the mid-19th century, has been of inestimable value in the development of chemistry .

It was not actually recognized until the second decade of the 20th century that the order of elements in the periodic system is that of their atomic numbers, the integers of which are equal to the positive electrical charges of the atomic nuclei expressed in electronic units. In subsequent years great progress was made in explaining the periodic law in terms of the electronic structure of atoms and molecules. This clarification has increased the value of the law, which is used as much today as it was at the beginning of the 20th century, when it expressed the only known relationship among the elements.

History of the periodic law

The early years of the 19th century witnessed a rapid development in analytical chemistry—the art of distinguishing different chemical substances—and the consequent building up of a vast body of knowledge of the chemical and physical properties of both elements and compounds . This rapid expansion of chemical knowledge soon necessitated classification , for on the classification of chemical knowledge are based not only the systematized literature of chemistry but also the laboratory arts by which chemistry is passed on as a living science from one generation of chemists to another. Relationships were discerned more readily among the compounds than among the elements; it thus occurred that the classification of elements lagged many years behind that of compounds. In fact, no general agreement had been reached among chemists as to the classification of elements for nearly half a century after the systems of classification of compounds had become established in general use.

J.W. Döbereiner in 1817 showed that the combining weight, meaning atomic weight , of strontium lies midway between those of calcium and barium , and some years later he showed that other such “ triads ” exist (chlorine, bromine , and iodine [halogens] and lithium , sodium , and potassium [alkali metals]). J.-B.-A. Dumas, L. Gmelin, E. Lenssen, Max von Pettenkofer, and J.P. Cooke expanded Döbereiner’s suggestions between 1827 and 1858 by showing that similar relationships extended further than the triads of elements, fluorine being added to the halogens and magnesium to the alkaline-earth metals, while oxygen , sulfur , selenium , and tellurium were classed as one family and nitrogen , phosphorus , arsenic , antimony , and bismuth as another family of elements.

Attempts were later made to show that the atomic weights of the elements could be expressed by an arithmetic function , and in 1862 A.-E.-B. de Chancourtois proposed a classification of the elements based on the new values of atomic weights given by Stanislao Cannizzaro’s system of 1858. De Chancourtois plotted the atomic weights on the surface of a cylinder with a circumference of 16 units, corresponding to the approximate atomic weight of oxygen. The resulting helical curve brought closely related elements onto corresponding points above or below one another on the cylinder, and he suggested in consequence that “the properties of the elements are the properties of numbers,” a remarkable prediction in the light of modern knowledge.

Classification of the elements

In 1864, J.A.R. Newlands proposed classifying the elements in the order of increasing atomic weights, the elements being assigned ordinal numbers from unity upward and divided into seven groups having properties closely related to the first seven of the elements then known: hydrogen , lithium, beryllium , boron , carbon , nitrogen, and oxygen. This relationship was termed the law of octaves, by analogy with the seven intervals of the musical scale.

Then in 1869, as a result of an extensive correlation of the properties and the atomic weights of the elements, with special attention to valency (that is, the number of single bonds the element can form), Mendeleev proposed the periodic law, by which “the elements arranged according to the magnitude of atomic weights show a periodic change of properties.” Lothar Meyer had independently reached a similar conclusion, published after the appearance of Mendeleev’s paper.

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• Science Fair Project Ideas for Kids, Middle & High School Students ⋅

Fun Experiments for the Periodic Table

Examples of Single Replacement Reactions

The periodic table makes rich ground for educational experiments that are also fun and often surprising. Since the elements of the periodic table include everything from the lightest gas known to man to the most dense and heavy metal, and since many of them are found in everyday objects, it's easy to find experiments that will entertain students as they learn about chemistry.

Overview of Elements

Explain that elements are substances that cannot be divided into simpler elements. If you keep cutting gold into smaller and smaller pieces, you will still have pure gold, even down to the quantity of one atom. However, few elements are as stable as gold and many are not found in a pure state in nature because they combine easily with other elements. Even a relatively stable element like iron will combine with oxygen if left unprotected and will eventually turn to iron oxide, known better as rust. One of the major purposes of chemistry is to extract pure elements from complex compounds for industrial and scientific purposes.

Combining Elements

Combining two or more elements can deliver some surprising results. For younger kids, mixing two clear gases, oxygen and hydrogen, will teach them a valuable lesson in an interesting way they'll remember. For older kids, add an alkali metal, such as sodium, to the oxygen and hydrogen to produce a small explosion. Have everyone wear safety gear for this particular experiment.

Isolating Elements

Elements, even some rare ones, can be found in combination with other elements in everyday products. For instance, lead can be found in products that darken gray hair and can be separated from the solution fairly easily. Another experiment that might confound kids is isolating copper from copper sulfate with electricity.

Many elements will react to the presence of air, fire or chemical compounds. One simple experiment is to isolate bubbles of hydrogen from water, then expose them to flame, causing small explosions. Some elements will react only in the presence of certain substances and then only with the greatest of difficulty. Demonstrate the story of the Danish scientists who saved two pure gold Nobel Prizes from the Nazis by dissolving them in aqua regia, a mixture of hydrochloric and nitric acids. Demonstrate the ability of hydrochloric acid to dissolve other metals, then place a small flake of gold in the acid. After a while, add nitric acid to the mix and observe what happens.

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How the Periodic Table of the Elements is arranged

The periodic table of the elements isn't as confusing as it looks.

• Periodic table groups

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Scientists had a rudimentary understanding of the periodic table of the elements centuries ago. But in the late 19th century, Russian chemist Dmitri Mendeleev published his first attempt at grouping chemical elements according to their atomic weights. There were only about 60 elements known at the time, but Mendeleev realized that when the elements were organized by weight, certain types of elements occurred in regular intervals, or periods.

Today, 150 years later, chemists officially recognize 118 elements (after the addition of four newcomers in 2016) and still use Mendeleev's periodic table of elements to organize them. The table starts with the simplest atom, hydrogen, and then organizes the rest of the elements by atomic number, which is the number of protons each contains. With a handful of exceptions, the order of the elements corresponds with the increasing mass of each atom.

The table has seven rows and 18 columns. Each row represents one period; the period number of an element indicates how many of its energy levels house electrons. Sodium, for instance, sits in the third period, which means a sodium atom typically has electrons in the first three energy levels. Moving down the table, periods are longer because it takes more electrons to fill the larger and more complex outer levels.

The columns of the table represent groups, or families, of elements. The elements in a group often look and behave similarly, because they have the same number of electrons in their outermost shell — the face they show to the world. Group 18 elements, on the far right side of the table, for example, have completely full outer shells and rarely participate in chemical reactions .

Elements are typically classified as either a metal or nonmetal, but the dividing line between the two is fuzzy. Metal elements are usually good conductors of electricity and heat. The subgroups within the metals are based on the similar characteristics and chemical properties of these collections. Our description of the periodic table uses commonly accepted groupings of elements, according to the Los Alamos National Laboratory .

Groups of the Periodic table

Alkali metals: The alkali metals make up most of Group 1, the table's first column. Shiny and soft enough to cut with a knife, these metals start with  lithium (Li) and end with  francium (Fr). They are also extremely reactive and will  burst into flame or even explode on contact with water, so chemists store them in oils or inert gases . Hydrogen, with its single electron, also lives in Group 1, but the gas is considered a nonmetal.

Alkaline-earth metals: The alkaline-earth metals make up Group 2 of the periodic table, from  beryllium (Be) through  radium (Ra). Each of these elements has two electrons in its outermost energy level, which makes the alkaline earths reactive enough that they're rarely found alone in nature. But they're not as reactive as the alkali metals. Their chemical reactions typically occur more slowly and produce less heat compared to the alkali metals.

Lanthanides: The third group is much too long to fit into the third column, so it is broken out and flipped sideways to become the top row of the island that floats at the bottom of the table. This is the lanthanides, elements 57 through 71 —  lanthanum (La) to  lutetium (Lu). The elements in this group have a silvery white color and tarnish on contact with air.

Actinides: The actinides line the bottom row of the island and comprise elements 89,  actinium (Ac), through 103,  lawrencium (Lr). Of these elements, only  thorium (Th) and  uranium (U) occur naturally on Earth in substantial amounts. All are radioactive. The actinides and the lanthanides together form a group called the inner transition metals.

Transition metals: Returning to the main body of the table, the remainder of Groups 3 through 12 represent the rest of the transition metals. Hard but malleable, shiny, and possessing good conductivity, these elements are what you typically think of when you hear the word metal. Many of the greatest hits of the metal world — including gold , silver , iron and platinum — live here.

Post-transition metals: Ahead of the jump into the nonmetal world, shared characteristics aren't neatly divided along vertical group lines. The post-transition metals are  aluminum (Al),  gallium (Ga),  indium (In),  thallium (Tl),  tin (Sn),  lead (Pb) and  bismuth (Bi), and they span Group 13 to Group 17. These elements have some of the classic characteristics of the transition metals, but they tend to be softer and conduct more poorly than other transition metals. Many periodic tables will feature a bolded "staircase" line below the diagonal connecting boron with astatine. The post-transition metals cluster to the lower left of this line.

Metalloids: The metalloids are  boron (B),  silicon (Si),  germanium (Ge),  arsenic (As),  antimony (Sb),  tellurium (Te) and  polonium (Po). They form the staircase that represents the gradual transition from metals to nonmetals. These elements sometimes behave as semiconductors (B, Si, Ge) rather than as conductors. Metalloids are also called "semimetals" or "poor metals."

Nonmetals: Everything else to the upper right of the staircase — plus  hydrogen (H), stranded way back in Group 1 — is a nonmetal. These include  carbon (C),  nitrogen (N),  phosphorus (P),  oxygen (O),  sulfur (S) and  selenium (Se).

Halogens: The top four elements of Group 17, from  fluorine (F) through  astatine (At), represent one of two subsets of the nonmetals. The halogens are  quite chemically reactive and tend to pair up with alkali metals to produce various types of salt. The table salt in your kitchen, for example, is a marriage between the alkali metal sodium and the halogen chlorine.

Noble gases: Colorless, odorless and almost completely nonreactive, the inert, or noble gases round out the table in Group 18. Many chemists expect oganesson (previously designated " ununoctium "), one of the four newly named elements, to share these characteristics; however, because this element has a half-life measuring in the milliseconds, no one has been able to test it directly. Oganesson completes the seventh period of the periodic table, so if anyone manages to synthesize element 119 (and  the race to do so is already underway ), it will loop around to start row eight in the alkali metal column.

Because of the cyclical nature created by the periodicity that gives the table its name, some chemists prefer to visualize  Mendeleev's table as a circle .

• Watch this brief video about the periodic table and element groups, from Crash Course .
• Flip through this interactive periodic table of elements at ptable.com .
• Check out this free, online educational resource for understanding elemental groups from CK-12 .

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Charlie Wood is a staff writer at Quanta Magazine, where he covers physics both on and off the planet. In addition to Live Science, his work has also appeared in Popular Science, Scientific American, The Christian Science Monitor, and other publications. Previously, he taught physics and English in Mozambique and Japan, and he holds an undergraduate degree in physics from Brown University. 

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Experimental student testing model slated for statewide rollout

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This spring marked a departure from the usual end-of-year testing regime at Missoula’s Hellgate Elementary School District. Gone were the back-to-back weeks of summative assessments students and teachers had grown accustomed to. Instead, the nine months leading up to this week’s final hours of instruction had been sprinkled with scaled-down tests designed to incrementally gauge students’ competence in math and reading.

The change wasn’t without its hiccups, Hellgate Superintendent Molly Blakely said, but overall, teachers in the district reported positively about their ability to manage student testing time and identify academic strengths and weaknesses in a more timely manner.

“Teachers really appreciated that the testlets were shorter, and so it felt more manageable time-wise,” Blakely told Montana Free Press. “And just being able to get the results and the data back in a timely fashion allows you to look at both weaknesses or gaps that students may have, as well as strengths. Because you’re getting that feedback in late October possibly, depending on when the testlet was given, then you’re able to adjust your instructional practices.”

All Montana public school students in grades 3 through 8 will soon follow the example set by Hellgate and roughly five dozen other districts across the state. After two years of piloting a new approach in those districts, the Office of Public Instruction is now preparing for a statewide rollout of the model this fall. According to OPI Chief Operating Officer Julie Murgel, Montana’s long-standing practice of administering a single test each spring will now give way to 12 smaller assessments, or testlets, conducted at various points throughout the school year.

“A testlet is almost more like a quiz, almost like a chapter assessment, if you will,” Murgel said. “What it’s doing is it’s assessing a bundle of [instructional] standards in the time of when they’re taught, at that moment.”

Murgel added that the testlets, which were crafted to align with state subject-area standards, must be administered within certain windows, but will ideally offer enough flexibility for individual districts and teachers to sync them with their local lesson plans.

State and local education officials have been gearing up for the switch for months, with OPI staff offering regular updates to the Montana Board of Public Education and fielding questions about continued modifications. The U.S. Department of Education requires that all public school students in grades 3 through 8 be tested in reading and math at the end of each school year, but granted Montana a one-year waiver last fall to accommodate OPI’s pilot project on the condition that the state implement its statewide field test in 2024-25 and adjust student achievement standards accordingly.

According to Roger Dereszynski, assessment director for the Billings Public Schools, the federal waiver helped resolve an issue faced by participating districts like his: double testing. Prior to the waiver, Dereszynski said, districts in the pilot’s first year were still required to administer end-of-year summative tests in order to comply with regulatory mandates. Billings participated in both years, a decision Dereszynski said was motivated by a desire to become familiar with a new testing model the state appeared likely to adopt in the future.

State ed officials explore periodic exams as alternative to year-end standardized tests

This fall, 20 school districts across the state are exploring a new approach to standardized testing. The Office of Public Instruction-led pilot, backed by $3 million in federal funding, seeks to replace Montana’s year-end exams with incremental tests throughout the school year.

Starting in spring 2022, OPI also spearheaded a state task force to review the pilot’s findings in collaboration with the National Center for the Improvement of Educational Assessment. In a virtual interview alongside Murgel, state Superintendent Elsie Arntzen said the end goal of the yearslong work is to craft an approach to testing that helps students recognize their academic growth and gives teachers timelier access to results that can inform classroom instruction.

“The very, very end of this is to have the student recognize what they learned and how they learned it, because that assessment is the how, right?” Arntzen said. “But then also for the student, if the student will own their own learning, then they will attend school more, they will be attentive to school because they’ll recognize growth themselves. It’s not the adult telling them, it’s the student owning their learning with the help of that mentor, that teacher.”

Student assessment has been the subject of much debate in Montana and nationally over the years. Critics of the traditional end-of-year testing model have argued that test results register too late in the year for teachers to make much practical instructional use of them. Blakely said the timing also presented challenges, with sick days or warm spring weather affecting student participation or focus during the school year’s only testing window. She added that the exam itself is “long, laborious, tedious,” requiring students to spend hours reviewing nine months of lessons on reading and math and bringing normal classroom activity to a lengthy halt.

“When you’re talking about doing assessments with students as young as third grade, it’s just not, in my opinion, developmentally appropriate to make an 8-year-old student sit and take a test for four straight days for math and English language arts, which was our previous testing model,” Blakely said. “With this, it just seems much more developmentally appropriate.”

Montana’s pilot program reflects the national conversation around reforming education’s approach to student assessment , a conversation partly rooted in the declining test scores reported across the country since the COVID-19 pandemic. But the change OPI is pushing is not without critics. 

Most recently, several district officials voiced concerns to the Montana Board of Public Education last month about test length, student fatigue and whether teachers are truly receiving testlet results in a timely enough fashion. Laurie Barron, superintendent of the Evergreen School District in Kalispell, told board members that while her staff is “wholly committed” to the pilot, the initiative has felt “extremely rushed” since its inception in 2022. She cautioned against Montana using any pilot data for school accreditation or federal accountability reporting, a warning she added would include next year’s statewide rollout, since that is still categorized as a pilot year.

“We are also very concerned about the length of time it is taking for the testlets,” Barron said. “Originally we were told they would be 15 to 20 minutes in length per testlet. We’re seeing an average of 30 to 50 minutes per testlet.”

Barron and others also expressed a desire for fewer testing windows throughout the year to reduce anxiety among students and teachers. However, they acknowledged that some of their concerns — namely the amount of time spent taking testlets and the roughly 10-day turnaround on results — will likely be ironed out as familiarity with the model grows and OPI works with its vendor, nonprofit assessment company New Meridian , to further improve the system.

Blakely and Dereszynski acknowledged experiencing similar growing pains during the pilot so far, and echoed their belief that ongoing refinement will likely address those issues. In the end, Dereszynski said, he can envision a future where the state-delivered testlets could serve as a replacement for the periodic assessments his district and others already deliver on their own. According to OPI officials, blending those local needs and practices with state standards and federal requirements is a primary driver for revisiting Montana’s whole approach to testing.

“We’ve all said for quite a while that we really need to improve this assessment system,” Murgel said. “Here’s an opportunity.”

Murgel and Arntzen confirmed that the statewide change will not affect testing at the high school level or administration of the ACT, a widely used college readiness exam that also serves as Montana’s federally mandated high school summative assessment. Concerns about income- and race-based score gaps coupled with the challenge of delivering such exams during the COVID-19 pandemic has led many American colleges and universities including the University of Montana and Montana State University to abandon requiring test scores as a condition of student admission. However, some prestigious institutions like Yale, Dartmouth and MIT have begun to reinstate the requirement in recent years, making the availability of standardized tests a prerequisite for high schoolers looking to apply to those campuses.

Though the ACT will remain in use in Montana for at least the next year, Murgel said the state’s student assessment debate has already begun to turn toward the high school level — a direction she partly attributed to a recent administrative change that shifted the cost of administering the ACT from the Office of the Commissioner of Higher Education to OPI.

“We’re not ready quite yet,” Murgel said, “but we’ve got to start thinking about what do we really want to see happening at that high school level and what does that mean for us?”

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2.3: Calculating Atomic Masses (Problems)

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\( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)

PROBLEM \(\PageIndex{1}\)

Determine the number of protons, neutrons, and electrons in the following isotopes that are used in medical diagnoses:

(a) atomic number 9, mass number 18, charge of 1−

(b) atomic number 43, mass number 99, charge of 7+

(c) atomic number 53, atomic mass number 131, charge of 1−

(d) atomic number 81, atomic mass number 201, charge of 1+

(e) Name the elements in parts (a), (b), (c), and (d)

p: 9; n: 9; e: 10

p: 43; n: 56; e: 36

p: 53; n: 78; e: 54

p: 81; n: 120; e: 80

a - F; b - Tc; c - I; d - Tl

PROBLEM \(\PageIndex{2}\)

Give the number of protons, electrons, and neutrons in neutral atoms of each of the following isotopes:

(a) \(\ce{^{10}_5B}\)

(b) \(\ce{^{199}_{80}Hg}\)

(c) \(\ce{^{63}_{29}Cu}\)

(d) \(\ce{^{13}_6C}\)

(e) \(\ce{^{77}_{34}Se}\)

p&e: 5; n: 5

p&e: 80; n: 119

p&e: 29; n: 34

p&e: 6; n: 7

p&e: 34; n: 43

PROBLEM \(\PageIndex{3}\)

An element has the following natural abundances and isotopic masses: 90.92% abundance with 19.99 amu, 0.26% abundance with 20.99 amu, and 8.82% abundance with 21.99 amu. Calculate the average atomic mass of this element.

PROBLEM \(\PageIndex{4}\)

Average atomic masses listed by IUPAC are based on a study of experimental results. Bromine has two isotopes, 79 Br and 81 Br, whose masses (78.9183 and 80.9163 amu) and abundances (50.69% and 49.31%) were determined in earlier experiments. Calculate the average atomic mass of Br based on these experiments. How does this compare to the value given on the periodic table?

79.90 amu; this matches the value on the periodic table

PROBLEM \(\PageIndex{5}\)

The 18 O: 16 O abundance ratio in some meteorites is greater than that used to calculate the average atomic mass of oxygen on earth. Is the average atomic mass of an oxygen atom in these meteorites greater than, less than, or equal to a terrestrial oxygen atom?

Greater, since the contribution to the average atomic mass of 18 O is greater, that will raise the average atomic mass in meteorites compared to on earth.

PROBLEM \(\PageIndex{6}\)

Compare 1 mole of H 2 , 1 mole of O 2 , and 1 mole of F 2 .

(a) Which has the largest number of molecules? Explain why.

(b) Which has the greatest mass? Explain why.

1 mole is always 6.022 x 10 23 molecules. They have the same number of molecules.

F 2 ; it has the highest molar mass.

PROBLEM \(\PageIndex{7}\)

Which contains the greatest mass of oxygen: 0.75 mol of ethanol (C 2 H 5 OH), 0.60 mol of formic acid (HCO 2 H), or 1.0 mol of water (H 2 O)? Explain why.

Formic acid. Its formula has twice as many oxygen atoms as the other two compounds (one each). Therefore, 0.60 mol of formic acid would be equivalent to 1.20 mol of a compound containing a single oxygen atom.

PROBLEM \(\PageIndex{8}\)

Determine the mass of each of the following:

(a) 0.0146 mol KOH (b) 10.2 mol ethane, C 2 H 6 (c) 1.6 × 10 −3 mol Na 2 SO 4 (d) 6.854 × 10 3 mol glucose, C 6 H 12 O 6 (e) 2.86 mol Co(NH 3 ) 6 Cl 3

1.235 × 10 6 g (1235 kg)

PROBLEM \(\PageIndex{9}\)

Which of the following represents the least number of molecules?

• 20.0 g of H 2 O (18.02 g/mol)
• 77.0 g of CH 4 (16.06 g/mol)
• 68.0 g of CaH 2 (42.09 g/mol)
• 100.0 g of N 2 O (44.02 g/mol)
• 84.0 g of HF (20.01 g/mol)

20.0 g of H 2 O represents the smallest number of moles, meaning the least number of molecules present. Since 1 mole = 6.022 × 10 23 molecules (or atoms) regardless of identity, the least number of moles will equal the least number of molecules.

Contributors

Paul Flowers (University of North Carolina - Pembroke), Klaus Theopold (University of Delaware) and Richard Langley (Stephen F. Austin State University) with contributing authors.  Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at http://cnx.org/contents/[email protected] ).

• Adelaide Clark, Oregon Institute of Technology

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Experimental study on local scour at the monopile foundation of an offshore wind turbine under the combined action of wave–current–vibration.

1. Introduction

2. experimental research program, 2.1. experimental layout, 2.2. key parameters of the experimental, 2.3. experimental scheme, 2.3.1. wave–current test conditions, 2.3.2. wave–current–vibration test conditions, 3. study on scour characteristics around a monopile under wave–current–vibration interaction, 3.1. the variation law of wave height and reference point velocity, 3.1.1. the variation law of velocity and wave height at the reference point under wave action.

• Water particle trajectory at the reference point;
• Wave height curve and horizontal velocity change at the reference point;

3.1.2. The Variation Law of Velocity and Wave Height at the Reference Point under the Action of Wave–Current

3.2. study on the development of the local scour depth of a monopile under the combined action of wave–current–vibration, 3.2.1. the influence of vibration frequency on the duration of scour depth development, 3.2.2. the influence of amplitude on the duration of scour depth development, 3.3. development process and morphological characteristics of the scour hole, 3.3.1. the development process of the scour hole under the combined action of current and vibration, 3.3.2. the development process of the scour hole under the action of current and vibration, 3.3.3. the development process of the scour hole under the action of current and vibration, 3.4. the influence of vibration load on the profile of the scour hole, 4. analysis of influencing factors on the local scour depth of a monopile under the combined action of wave–current–vibration, 4.1. the influence of vibration intensity on the maximum scour depth, 4.2. the influence of the froude number fr on the maximum scour depth, 4.3. the influence of the kc number on the maximum scour depth, 4.4. effect of u cw on the maximum scour depth, 4.5. empirical formula of local scour depth of a monopile under combined action of wave–current–vibration, 5. conclusions, author contributions, institutional review board statement, informed consent statement, data availability statement, conflicts of interest.

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• Wu, M.; Stratigaki, V.; Fazeres-Ferradosa, T.; Rosa-Santos, P.; Taveira-Pinto, F.; Troch, P. Experimental Uncertainty Analysis of Monopile Scour Protection Stability Tests. Renew. Energy 2023 , 210 , 174–187. [ Google Scholar ] [ CrossRef ]
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Share and Cite

Shi, L.; Cheng, Y.; Zheng, Y.; Xia, B.; Huang, X. Experimental Study on Local Scour at the Monopile Foundation of an Offshore Wind Turbine under the Combined Action of Wave–Current–Vibration. J. Mar. Sci. Eng. 2024 , 12 , 963. https://doi.org/10.3390/jmse12060963

Shi L, Cheng Y, Zheng Y, Xia B, Huang X. Experimental Study on Local Scour at the Monopile Foundation of an Offshore Wind Turbine under the Combined Action of Wave–Current–Vibration. Journal of Marine Science and Engineering . 2024; 12(6):963. https://doi.org/10.3390/jmse12060963

Shi, Li, Yongzhou Cheng, Yuwei Zheng, Bo Xia, and Xiaoyun Huang. 2024. "Experimental Study on Local Scour at the Monopile Foundation of an Offshore Wind Turbine under the Combined Action of Wave–Current–Vibration" Journal of Marine Science and Engineering 12, no. 6: 963. https://doi.org/10.3390/jmse12060963

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