conclusion of flame test experiment

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Flame Test Colors and Procedure (Chemistry)

The flame test is an analytical chemistry technique that helps identify elements in samples based on their characteristic emission spectra. Mostly the flame test detects metal ions, but some nonmetals color flames as well.

How the Flame Test Works

The basic premise is that heat from a flame gives atoms enough energy that their electrons become excited. Dropping to a more stable energy state involves the release of photons . These photons have a frequency (light color) that is a characteristic of the element.

However, not all elements release light in the visible portion of the spectrum. Some elements don’t change a flame’s color at all. For example, gold, silver, platinum, and palladium do not yield a flame test result. However, some of these metals produce sparks in a flame and other deposit pure metal onto a surface.

Advantages and Disadvantages of the Flame Test

The flame test offers both advantages and disadvantages as an analytical technique.

• Extremely quick and easy
• Only requires a tiny sample
• Good at eliminating possible elements in a sample
• Visually appealing, so it’s great at raising student interest in science

Disadvantages

• Does not definitively identify a sample
• Results are subjective
• Results are highly susceptible to contamination, particularly from sodium
• Several elements yield approximately the same color results
• Some samples yield brighter colors than others
• Results vary somewhat depending on the exact chemical composition of the sample and the fuel
• Qualitative rather than quantitative technique
• Does not work with extremely dilute samples

The bead test is a related technique. Better techniques include flame photometry, flame emission spectroscopy, and flame absorption spectroscopy. However, these methods are quite a bit more expensive.

How to Do the Flame Test

There are several ways of performing the flame test.

• Dissolve the sample in water or another solvent , soak a wooden splint in the liquid, and let it dry.
• Dip a Nichrome wire into a solid or liquid sample.
• Make a paste of a solid sample with hydrochloric acid (HCl) and dip a splint or wire into the paste.
• Dip a cotton swab into the sample. (This method is prone to sodium contamination.)
• Dissolve the sample in a small amount of methanol. Dip a bit of melamine sponge (e.g., Magic Eraser) into the sample.

Options for the flame include a candle flame, Bunsen burner flame, or gas flame.

Basically, you dip a wire or splint into a solid sample or its solution and expose the sample to a colorless flame. Viewing the results through a cobalt blue glass filters out excess yellow and makes identification a bit easier. Once you have a color, compare it to a table of flame test colors.

Make Colored Fire

The flame test is the basis for firework colors , colored fire spray bottles , and colored campfires .

Table of Flame Test Colors

This is a table of flame test colors, ordering the elements alphabetically by symbol.

• Barrow, R. F.; Caldin, E. F. (1949). “Some Spectroscopic Observations on Pyrotechnic Flames”. Proceedings of the Physical Society . Section B. 62 (1): 32–39. doi: 10.1088/0370-1301/62/1/305
• Landis, Arthur M.; Davies, Malonne I.; Landis, Linda; Thomas, Nicholas C. (2009). “‘Magic Eraser’ Flame Tests”. Journal of Chemical Education . 86 (5): 577. doi: 10.1021/ed086p577
• Patnaik, Pradyot (2002).  Handbook of Inorganic Chemicals . McGraw-Hill. ISBN 0-07-049439-8.
• Sanger, Michael J.; Phelps, Amy J.; Banks, Catherine (2004). “Simple Flame Test Techniques Using Cotton Swabs”. Journal of Chemical Education . 81 (7): 969. doi: 10.1021/ed081p969

Related Posts

How to Do Flame Tests for Qualitative Analysis

How to Do a Flame Test & Interpret Results

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The flame test is used to visually determine the identity of an unknown metal or metalloid ion based on the characteristic color the salt turns the flame of a Bunsen burner. The heat of the flame excites the electrons of the metals ions, causing them to emit visible light. Every element has a signature emission spectrum that can be used to differentiate between one element and another.

Key Takeaways: Perform the Flame Test

• The flame test is a qualitative test in analytical chemistry used to help identify the composition of a sample.
• The premise is that heat gives energy to elements and ions, causing them to emit light at a characteristic color or emission spectrum.
• The flame test is a quick way to narrow down the identity of a sample, but must be combined with other tests to confirm composition.
• How to Do the Flame Test

Classic Wire Loop Method First, you need a clean wire loop. Platinum or nickel-chromium loops are most common. They may be cleaned by dipping in hydrochloric or nitric acid, followed by rinsing with distilled or deionized water . Test the cleanliness of the loop by inserting it into a gas flame. If a burst of color is produced, the loop is not sufficiently clean. The loop must be cleaned between tests.

The clean loop is dipped in either a powder or solution of an ionic (metal) salt. The loop with sample is placed in the clear or blue part of the flame and the resulting color is observed.

Wooden Splint or Cotton Swab Method Wooden splints or cotton swabs offer an inexpensive alternative to wire loops. To use wooden splints, soak them overnight in distilled water. Pour out the water and rinse the splints with clean water, being careful to avoid contaminating the water with sodium (as from sweat on your hands). Take a damp splint or cotton swab that has been moistened in water, dip it in the sample to be tested, and wave the splint or swab through the flame. Do not hold the sample in the flame as this would cause the splint or swab to ignite. Use a new splint or swab for each test.

How to Interpret Flame Test Results

The sample is identified by comparing the observed flame color against known values from a table or chart.

Red Carmine to Magenta: Lithium compounds. Masked by barium or sodium. Scarlet or Crimson: Strontium compounds. Masked by barium. Red: Rubidium (unfiltered flame) Yellow-Red: Calcium compounds. Masked by barium.

Yellow Gold: Iron Intense Yellow: Sodium compounds, even in trace amounts. A yellow flame is not indicative of sodium unless it persists and is not intensified by an addition of 1% NaCl to the dry compound.

White Bright White: Magnesium White-Green: Zinc

Green Emerald: Copper compounds, other than halides. Thallium. Bright Green: Boron Blue-Green: Phosphates, when moistened with H 2 SO 4 or B 2 O 3 . Faint Green: Antimony and NH 4 compounds. Yellow-Green: Barium, manganese(II), molybdenum.

Blue Azure: Lead, selenium, bismuth, cesium, copper(I), CuCl 2 and other copper compounds moistened with hydrochloric acid, indium, lead. Light Blue: Arsenic and some of its compounds. Greenish Blue: CuBr 2 , antimony

Purple Violet: Potassium compounds other than borates, phosphates, and silicates. Masked by sodium or lithium. Lilac to Purple-Red: Potassium, rubidium, and/or cesium in the presence of sodium when viewed through a blue glass.

Limitations of the Flame Test

• The test cannot detect low concentrations of most ions .
• The brightness of the signal varies from one sample to another. For example, the yellow emission from sodium is much brighter than the red emission from the same amount of lithium .
• Impurities or contaminants affect the test results. Sodium , in particular, is present in most compounds and will color the flame. Sometimes a blue glass is used to filter out the yellow of sodium.
• The test cannot differentiate between all elements. Several metals produce the same flame color. Some compounds do not change the color of the flame at all.

Because of the limitation, the flame test might be used to rule out the identity of an element in a sample, rather than definitively identify it. Other analytical procedures should be conducted in addition to this test.

Flame Test Colors

This table lists the expected colors for elements in the flame test. Obviously, the names of the colors are subjective, so the best way to learn to recognize close-colored elements is to test known solutions so you know what to expect.

• Lange's Handbook of Chemistry , 8th Edition, Handbook Publishers Inc., 1952.
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The Flame Test

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The Flame Test is a safer version of the traditional Rainbow Demonstration , an exercise popularly conducted in chemistry classrooms. The purpose of The Flame Test is to demonstrate to students the variety of colors produced when different metals or salts meet a flame. It contributes to their understanding of:

• Electromagnetic Spectrum
• Atomic structure
• Atomic spectra
• Visible light spectrum

Back-to-School Safety

• Joint Statement from the CSB and ACS: The Importance of Laboratory Safety in the Classroom  [PDF]
• Guidelines for Chemical Laboratoy Safety in Secondary Schools [PDF]

A Safer "Rainbow Flame" Demo for the Classroom

Developed by the American Association of Chemistry Teachers (AACT)

By the end of this demonstration, students should be able to:

• Use flame tests to identify a metal or metallic salt by the color that it produces when it is put into a flame.
• Calculate the frequency of light given its wavelength.
• Calculate the wavelength of light given its frequency.
• Identify an unknown metal by the color it emits when passed through a flame.

Instructions for Conducting the Flame Test

Exercise extreme caution around large containers of flammable liquids in the presence of an ignition source. Flame jetting can occur, causing flames to shoot out 15 feet or more.

More about Flame Jetting

Companion Resources for the Flame Test

• Playing with Fire: Chemical Safety Expertise Required ( Journal of Chemical Education - free access through 2018)
• Safety Data Sheets: Information That Could Save Your Life ( ChemMatters )
• Teacher's Guide [DOCX] ( ChemMatters )
• Key Lessons for Preventing Incidents from Flammable Chemicals in Educational Demonstrations (Chemical Safety Board)

More about the Traditional Rainbow Demonstration

Notice: ACS's Committee on Chemical Safety recommends that the “Rainbow” demonstration on open benches involving the use of flammable solvents such as methanol be discontinued immediately due to extreme risk of flash fires and flame jetting.  

• Safety Alert: The Rainbow Demonstration [PDF] (ACS, Committee on Chemical Safety)
• How To Make Chemistry Classroom Demonstrations And Experiments Safer ( C&EN )

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Flame Test Lab Conclusion

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Flame tests using metal salts

In this classic science experiment, students report on the colours produced when flame tests are carried out on different metal salts.

Student Sheet

In this practical I will be:

• Observing and recording the findings of the practical
• Providing oral and written explanations of my observations, based on scientific evidence and understanding.
• Comparing and grouping materials on the basis of their observable properties.

Introduction:

A local priest has claimed that he has the ability to directly talk to the gods, such as Anubis and Osiris. As an ancient Egyptian science-artist you are highly sceptical of his claims. After going to see this priest it turns out that he is turning flames different colours by throwing different ground minerals on to the flame. Obviously it isn’t the gods’ doing but you are intrigued as to what is happening. You decide to investigate further…

(Wear safety glasses and tie back long hair)

• Saturated calcium ethanoate solution (must be saturated)
• Ethanol (IDA)
• Lithium chloride (LiCl) solution in a spray bottle; 1 spatula amount in 100 cm 3 water
• Copper(II) chloride (CuCl2) solution in a spray bottle;1 spatula amount in 100 cm 3 water
• Sodium chloride (NaCl) solution in a spray bottle; 1 spatula amount in 100 cm 3 water
• 2 heat resistant mats
• 1 beaker (250 cm 3 )
• Lithium chloride (LiCl) solution in a beaker; 1 spatula amount in 100 cm 3 water
• Copper(II) chloride (CuCl2) solution in a beaker; 1 spatula amount in 100 cm 3 water
• Sodium chloride (NaCl) solution in a beaker; 1 spatula amount in 100 cm 3 water
• 1 heat resistant mats
• Bunsen burner
• 12 cm length of nichrome or platinum wire

The following solutions each in a 250 cm 3 conical flask:

2 M calcium chloride (IRRITANT)

1 M copper(II) chloride (IRRITANT)

2 M lithium chloride (IRRITANT)

2 M potassium chloride (low hazard)

1 M strontium chloride (IRRITANT)

2 M sodium chloride (low hazard)

• Plenty of spills soaked in water overnight.
• Bunsen burners or adjustable commercial blow torch
• Pour 50 cm 3 of the saturated calcium ethanoate solution into the 250 cm 3 beaker. Carefully add ethanol to the calcium ethanoate.
• Stir until a solid is formed. If no solid is formed add more ethanol.
• Using a spatula carefully lift out the solid and place it on a heat resistant mat. 
• Let it stand for a minute to allow it to dry enough to be lit.
• Use a lighted splint to light the solid.
• Spray the flame with the lithium salt solution. Note the colour and record the result.
• Spray with the copper salt solution. Note the colour and record the result.
• Spray with the sodium salt solution. Note the colour and record the result.
• Put the flame out by carefully placing the other heat resistant mat on top of it.
• Take the nichrome or platinum wire and create a small loop at the end by bending the wire.
• Light the Bunsen burner.
• Turn the collar on the Bunsen burner so that you have an invisible or pale blue flame.
• Burn the loop end of the wire to remove any dust.
• Dip the loop into the lithium salt solution.
• Observe and record the colour seen.
• Burn the loop end of the wire to remove any lithium salt.
• Dip the loop into the copper salt solution.
• Burn the loop end of the wire to remove any copper salt.
• Dip the loop into the sodium salt solution.
• Put a dry spill into each of the metal salt solutions in conical flasks and leave.
• Use a dry spill to light the Bunsen. 
• Take one of the spills from one of the conical flasks containing a metal salt solution.
• Wave your spill over the Bunsen flame and observe its colour. Then extinguish the used spill and dispose of it. 
• Record the metal salt solution and the flame colour.
• Repeat steps 2 to 4 for each of the other metal salt solutions you have been provided with.

Calcium ethanoate is a very hygroscopic solid. This means it absorbs and coordinates with water very easily. When ethanol is added to a saturated aqueous solution of calcium ethanoate it forms a white gel. This is because the calcium ethanoate is relatively insoluble in ethanol, as opposed to water, so it precipitates as an inflammable solid, a firelighter that burns with a very clear flame so that any colour given to the flame is due to the metal ion in the salt solution.

When a metal salt solution is sprayed onto the flame the electrons in the metal are excited and jump from one electron shell level to the next highest shell level. They are said to be excited . They cannot remain there so as they return to the original shell, known as the grounded state the energy gained is lost in the form of light known as emission .

The colour of the light depends upon the metal (lithium(I) gives a magenta red-pink flame, calcium an orange red flame, potassium a lilac flame, strontium a crimson red flame, copper(II) gives a blue or green flame and sodium(I) gives a yellow flame). These colours are also often used in fireworks to give the different colours we see when they burn. Sodium is also used in some street lights and that is why they appear yellow when on. 

If the flame is looked at through a spectroscope it will give a characteristic spectrum. This is used in chemistry to analyse a material for type and concentration of atoms. Chemists ‘burn’ the substance and measure the frequency (colour) of the light given out. This process is called Atomic Emission Spectroscopy.

Teacher and Technician Sheet

In this practical students will:

• Observe and record the findings of the practical
• Provide oral and written explanations of their observations, based on scientific evidence and understanding.
• Compare and group materials on the basis of their observable properties.

This is an old and tested experiment but when dealing with colour and chemistry it would be difficult to leave it out – particularly if spectroscopy is to be considered.

It is possible to create a variety of coloured flames by burning a small amount of different metal salts in a fire. This is the basis of fireworks.

In chemistry terms the fact some metals burn with a characteristic flame colour is important since it allows us to introduce the concept of spectroscopy.

As an introduction fireworks might be a good starting point. A discussion could begin with what it is that makes them spectacular and lead to the types of effects seen in fireworks, especially the colours.

Curriculum range:

This activity is designed for secondary age students but could be used with upper primary pupils. It links with:

• reporting on findings from enquiries, including oral and written explanations, displays or presentations of results and conclusions;
• using straightforward scientific evidence to answer questions or to support their findings;
• comparing and grouping together materials on the basis of their properties;
• building a more systematic understanding of materials by exploring; and comparing the properties of a broad range of materials.

Going further:

Working pairs students can look at the flame colour using a spectroscope which can be a laboratory one or one they build themselves. There are directions to be found by clicking here .

Hazard warnings:

Calcium ethanoate – Low hazard

Ethanol (IDA) – Flammable may be harmful by inhalation, ingestion or skin absorption may act as an irritant. 

Lithium chloride – Solid is Acute Toxin Cat 4 (HARMFUL) 

Copper(II) chloride – Acute Toxin Cat 4 (HARMFUL) and a SKIN/EYE IRRIRANT (Cat 2) and HAZARDOUSTO THE AQUATIC ENVIRONMENT WITH LONG LASTING EFFECTS (cat 1)

Sodium chloride – No significant risk (Low Hazard)

Potassium chloride – No significant risk (Low Hazard)

Strontium chloride – Can cause SERIOUS EYE DAMAGE (Cat 1) and is a SKIN IRRITANT (Cat 2) and a RESPIRATORY IRRITANT.

Safety goggles and should be worn. Long hair should be tied back and secured when using naked flames in a laboratory.

Avoid permanganates, nitrates and chlorates. These produce harmful by-products when burned.

Equipment for method 1:

• Copper(II) chloride (CuCl2) solution in a spray bottle; 1 spatula amount in 100 cm 3 water

Equipment for method 2:

• 1 heat resistant  mats

Equipment for method 3:

• 2 M calcium chloride (SKIN/EYE IRRITANT)
• 1 M copper(II) chloride (SKIN/EYE IRRITANT)
• 2 M lithium chloride Low hazard
• 2 M potassium chloride (Low Hazard)
• 1 M strontium chloride (SKIN IRRITANT, EYE DAMAGE)
• 2 M sodium chloride (Low Hazard)
• Bunsen burners
• Heatproof mats

Technical notes:

This experiment can be accompanied by the RSC’s Flame Colours – a demonstration carried out by the teacher as instructed.

The teacher demonstration is the only time that ethanol should be near a naked flame.

The metal salt solutions can be made and stored in conical flasks stoppered with rubber bungs prior to using. 

Some spills are soaked in water to ensure that the flame colour can be observed properly before the spill burns away and reduces the risk of burning to the student.

When preparing for use, the excess water can be squeezed from the spills that have been soaking in water overnight before placing some of them in each of the conical flasks containing the metal salt solutions. 

Beakers (or similar) containing water could be provided for the students to use to extinguish their spills.

Method 3 is very easy to set up and use. 

It is safe from Year 7 upwards and the teacher demonstration suggested can accompany it. 

The students should be able to observe and record the relevant flame colours and understand the reasons behind this from the accompanying notes. 

Cobalt blue glass can be provided if available. The metal salt’s flame colour may be observed more easily when the yellow light is absorbed by the blue in the glass.

Lithium – magenta red flame

Calcium - orange red flame

Potassium - lilac flame

Strontium – crimson red flame

Copper – blue or green flame (depends on the copper used)

Sodium - yellow flame

The accompanying notes may need to be adjusted depending upon whether all the method options are provided or not.

Flame tests using metal salts: student sheet

Flame tests using metal salts: teacher sheet.

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Introduction

The flame test is one of the most commonly used analytical processes in chemistry. It is widely used to detect and analyze the presence of certain elements in the given salt or compound. Primarily, the flame test detects the presence of metal ions in a compound, and as ions of each element have a specific characteristic based in their emission spectrum, the flame test for every element is different and distinctive.

This distinction is shown by the color of flames given out when the salt containing certain metal ions is burnt.

It is important to note here that the emission spectrum of each element that determines the flame color involves atoms instead of ions. The transition of electrons in the atoms tends to produce the visible color lines which are seen in the flame test.

Chemistry Behind Flame Test

The chemistry behind the flame test is simple. As we know that when an atom or ion is excited by heating to high temperatures, the electrons are promoted from their normal unexcited state into other orbitals, known as higher orbitals, as they have higher energy as compared to the normal or ground state orbitals.

When these excited electron falls back down to lower levels which can happen simultaneously or in several steps, the energy they have absorbed is released. This energy is released in the form of light.

Each jump involves the release of a specific amount of energy in the form of light. And each transition from higher to lower orbital corresponds to a frequency or wavelength.

All these jumps or transitions result in the formation of a spectrum of lines. Some of these lines are part of the visible part of the spectrum.

And the final color we see is a combination of all these individual colors. This color is the distinctive color of the element we observe in the flame test.

For instance, in the case of potassium or sodium ions or many other metal ions, the transition of electrons involves very high energies. This result in lines that fall in the UV part of the spectrum which is invisible to the naked eye.

This explains the role of atoms rather than ions to be the basis of flame test.

And the jumps we can see in flame tests are due to falling of electrons from a higher to a lower level in the metal atoms.

When we put sodium chloride, containing sodium ions, into a flame, the sodium atoms are formed as a result of certain sodium ions that regain their electrons and produce neutral sodium atoms again.

The orbitals and their configuration are very important features in each element with respect to a flame test.   

The structure of the unexcited state of sodium atom 1s 2 2s 2 2p 6 3s 1 and within the flame, there are different sorts of excited states of the electrons.

Sodium gives a bright orange-yellow flame color. This results from promoted electrons falling back from the 3p 1 level to their normal 3s 1 level.

The exact size of the potential energy jumps varies from one metal to another.

This means that each metal will have a different pattern of spectral lines, and so have a distinct flame color.

The elements of the Group1 are the easiest metals that can be accurately identified using the flame test.

For other metals, flame test does not provide a definitive identification, however, it gives a general idea of the probable compound.

Practical Process Detail

The procedure of this test is simple as it involves introducing sample of the compound or element to a non-luminous, hot flame, and examining the color of the resulting flame.

The flame test is an easy experiment to set up and is often conducted in science classes.

The principle of the test is that the atoms of the sample evaporate and as they are hot, they give off light when present in the flame.

A mixture of samples of a large amount of sample can also emit light. But such light is not good for identification analysis.

As described earlier, the individual atoms of a sample that are present in the flame emit light due to the transitions of electron between different atomic energy levels. Such transitions emit light that has very specific frequencies, and which is the characteristic of the chemical element.

Hence, the flame gets the color. And it is determined by the characteristics and properties of the chemical element of the material that is introduced into the flame.

There are certain points that need to be followed to obtain precise results in a flame test.

For instance, the samples are carried on a platinum wire, which is repeatedly cleaned with hydrochloric acid (HCl) to remove traces of any elements.

The compound to be assessed is usually made into a paste with concentrated hydrochloric acid, as it is volatile, and give good quality results.

It is also recommended to use different flames to avoid errors in the results due to contaminated flames, and to confirm the precision of the color.

The presence of sodium is considered as a common component in many compounds. And its spectrum is likely to dominate the light spectrum of other elements. To avoid this, the test flame is often viewed using a cobalt blue glass that filters out the yellow of sodium and allows the accurate presentation of color of other metal.

Flame Test Results of Common Elements

Here is the list of most common elements that are detected through the flame test. They have a distinct emission spectrum that allows them to show specific colored flame in a flame test. However, the colors given in the table are only a guide as colors are perceived differently by different people.

Certain precious metals, including platinum, titanium, palladium, gold, and silver do not produce a distinctive flame color. However, some can produce sparks when exposed to hot flame.

Safety Notes

The flame test can be dangerous if proper protocol and safety measures are not taken. It is advised to use good safety techniques.  We should wear a chemical apron and good quality chemical splash resistant goggles. It is also important that we practice the flame test under the supervision of a teacher.  

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Flame Test Experiment & Metal Ions | Usage & Results

Chase is a 14 year veteran science teacher with a specialization is chemistry/STEM. He has a Bachelors Degree in Chemistry and a Master's Degree in Instructional Media with a specialization in STEM.

Amanda has taught high school science for over 10 years. She has a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. She is also certified in secondary special education, biology, and physics in Massachusetts.

Table of Contents

How does the flame test work, how to use the flame test, lesson summary, how does the flame test work.

When an unknown chemical containing a metal ion is placed in a flame, the electrons become excited and jump energy levels. When the energy is released, it gives off energy in the form of light. The color of the light is unique to the element which emitted it.

What is a flame test and why is it used?

Flame tests are used in a chemistry lab as a method of determining an unknown substance which contains a metal. By placing the unknown in a flame, it will emit a specific color of light which can help to identify the unknown.

Take a lookup into the sky during a firework show and just imagine; each and every one of the vibrant colors that can be seen is the direct result of a specific chemical being ignited. There are several different metal ions inside of the firework that when ignited, release an array of different colors.

The concept of fireworks has been done on a much smaller scale in a chemistry lab for decades in the form of flame tests . A flame is a method of determining the identity of an unknown metal compound.

How To Identify Metals?

Metal ions look very similar to one another in the solid state in many cases. In order to identify them, chemical means are often necessary. By using a flame test, several chemicals which look physically similar can be identified from one another.

A flame test relies on an unknown chemical being placed into an open flame. Depending upon which color of light is emitted by the chemical as it is put into the flame, a scientist can then use the color emitted to determine the type of chemical present.

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• 0:04 What Is a Flame Test?
• 0:55 How Does the Flame Test Work?
• 2:49 How Do You Use a Flame Test?
• 3:56 Lesson Summary

Flame tests rely on the unique electron configurations of each and every element in order to identify them. When in compounds as these elements often are, they exist in the form known as an ion . A metal ion exists when the atom releases its valence electrons to bond with a non-metal atom as an ionic bond. The electrons of the ion surround the nucleus in the form of orbitals. Each orbital exists at a specific energy level, where electrons tend to be near at all times.

The metal ion is placed into an open flame, such as a Bunsen Burner , the electrons inside of the ions become excited. The excitement stems from the added energy to the compound, and that energy being absorbed by the ion. The electrons of the ion absorb the energy and the electron will jump up an energy level. Within moments, the energy is released by the electron in order to drop back down to its ground state. The released energy is visible to the human eye in the form of unique wavelengths of light. Each metal ion releases just slightly different wavelengths of light due to each element having its own unique electron configuration. The image shows the general concept of an atom that has electrons in several different orbital locations and energy levels. The arrow in the image represents the idea of the absorption and release of energy which causes a jump and then returns to the ground state.

Flame Color of Some Metal Ions

While there are too many metal ions to list all of the individual colors that are emitted during a flame test, there are some famous elements that are very well known for their colors. For example, sodium is known to produce a vibrant orange color when exposed to a flame. There are dozens of different metal ions possible in chemistry, but some of the most famous and the colors associated with them are found in the following table:

A flame test has some very specific uses in a chemistry lab. While it is visually pleasing to see all of the colors that different metals can produce, traditionally, this method is used to determine the identity of an unknown compound containing metals. By comparing the results of the test to known colors for each element, it is possible to identify the metal ion.

Here is a step by step procedure on how to perform a flame test:

• Obtain a sample of an unknown compound
• Put that unknown sample into what is known as a loop, which holds the sample in place
• Light a Bunsen Burner burner flame to a moderate flame height. It should not be too high or too low to ensure the best color
• Place the loop into the flame for a few seconds to ensure the electrons fully absorb the needed energy
• Observe/record the color of the flame as it is still located inside of the Bunsen Burner flame
• Compare the result of the flame test to a list of known accepted colors to determine the unknown
• Be sure to clean the loop thoroughly after each use by dunking it in acid and rinsing it with water to ensure there is no contamination of chemicals for future tests.

Flame tests are a visually exciting way to determine the identity of an unknown metal ion in a compound. Metals in a compound have established their ionic form, which means they have an electric charge. Unfortunately, most metal ions look very similar physically and it can be difficult to distinguish one from the next. A flame test can identify the metal-based off of the wavelength of light that is produced when placed into a flame. The table shows some of the more famous metal ions which exist and the colors associated with the flame test.

The metal ion goes through exc21qitation of the electrons in their orbitals from the flame. As the electrons try to return to their original ground state, they release energy in the form of light. Each element emits a specific wavelength of light due to the unique electron configurations of each. These specific wavelengths of light are visible to humans in the form of colors.

Video Transcript

What is a flame test.

Picture a New Year's Eve celebration. You can't wait to see the fabulous fireworks display. As you all count down to the New Year, bursts of light dazzle the sky. Bright reds, oranges, blues, and greens explode, leaving a light haze in the air.

Have you ever thought about what makes those brilliant colors? Surprisingly, all that fun comes down to chemistry. Inside fireworks are different metals, and when they are ignited they give off different colored light.

Chemists use this same principle to determine the identity of unknown metals using a flame test. During a flame test , chemists take an unknown metal and put it under a flame. The flame will turn different colors based on which metal is in the substance. The scientists can then identify their unknown substance. Let's take a detailed look at how this works.

How Does the Flame Test Work?

Metals are composed of individual atoms, which contain a nucleus of protons and neutrons and outer shells of electrons, which float freely around the nucleus. Metal atoms usually exist as ions , or an atom with a charge. Metal ions are usually cations, meaning they carry a positive charge.

The electrons of metal ions circle the nucleus in layers called orbitals . As the orbitals get farther away from the nucleus, their energy level increases. Electrons need to absorb energy to move to a higher energy orbital.

As it turns out, this is exactly what happens during the flame test. During the flame test, metal ions are exposed to thermal energy, or heat, from the flame. The electrons in the outer orbital absorb the energy and temporarily bounce to a higher energy level. However, the electrons don't stay put there. Eventually, they fall back to their original, ground energy level. As they fall back to the lower energy level, they release the energy they absorbed as light.

Light can be all different colors, depending on a property of light waves, called wavelength. Wavelength is the distance between peaks on the light waves. Light with longer wavelengths appears red, and light with shorter wavelengths appears purple.

Metals all have different configurations of electrons, which will produce different wavelengths of light during the flame test. The different wavelengths are seen as different colors. Thus, each particular metal will give off a characteristic color of light, which makes the flame change colors. Lithium is a metal that produces light with a longer wavelength during the flame test, which makes the flame turn red. Substances containing sodium turn orange, while substances containing calcium turn more of a yellow-red color. Substances with potassium ions produce a light purple flame and copper produces a characteristic blue-green color.

How Do You Use the Flame Test?

So now that you're excited about the flame test, let's learn how to use it safely. Like any experiment involving chemicals and heat, you'll need to take all the safety precautions. Use heat resistant gloves, goggles, and a chemistry apron to protect yourself. Be extremely careful when using the flame and always move anything flammable away from your workspace. If you have long hair, be sure to tie it back so it doesn't swing into the flame.

First, make sure your flame test loop is totally clean. If it has any residue on it, it could affect the color of the flame and your results. If your loop needs to be washed first, you can dip it in acid and then rinse with water and dry.

Next, light your bunsen burner after carefully connecting it to the gas. Make sure the flame isn't too low, but not so high that it's blowing in the air. Dip your clean loop into your substance and bring the loop to the edge of the flame. Pass it through the flame and observe the color change. You can then look at a table of known color changes to decide which metal is contained in your substance.

Metal ions are positively charged atoms that give off a characteristic color during the flame test . When thermal energy is absorbed by the electrons in the metal ion, they jump to a higher orbital . When they fall back to their ground level orbital, they release energy as light. Each metal ion has a unique configuration of electrons, so each metal releases light of a different wavelength , which corresponds to a different color.

To perform the flame test, dip a clean loop into the substance and pass it through a flame, observing the color. Then compare the color to the known emissions of different metal ions.

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Flame Test Analysis of Metallic Ions and their Applications

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Introduction

The purpose of this lab was to investigate the characteristic colors produced by metallic ions in a flame test and utilize this information to identify other elements. Additionally, this experiment aimed to provide insights into the principles behind fireworks.

A flame test is a technique used to identify specific metals in compounds or individual elements. When an electron transitions to a higher energy state, the element becomes excited, emitting light. As the electron returns to a lower energy state, it releases energy in the form of visible light, resulting in a flame color.

In some cases, multiple flame colors can be observed due to electrons transitioning between different energy levels. Each element exhibits a unique set of flame colors, which can be represented in a bright line spectra. This distinctive spectra enables the identification of elements based on their emitted colors.

When dealing with an unknown compound, previous data from similar tests can be used to match the observed flame color, helping to determine the metal present.

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Flame tests are also useful in selecting the desired colors for fireworks by using metals that emit specific colors. In this experiment, consistent materials and safety precautions were employed to ensure accurate and safe results.

• Chemical Splash Goggles
• Barium Nitrate (Ba(NO 3 ) 2 )
• Copper Nitrate (Cu(NO 3 ) 2 )
• Strontium Nitrate (Sr(NO 3 ) 2 )
• Lithium Nitrate (Li(NO 3 ))
• Potassium Nitrate (K(NO 3 ))
• Sodium Chloride (NaCl)
• Calcium Nitrate (Ca(NO 3 ) 2 )
• Nichrome wire loop
• Beaker, 50-ml
• Hydrochloric Acid
• Wash Bottle with distilled water
• Unknown Solution

Experimental Procedure

The following steps were followed in the experiment:

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• The spatula was cleaned thoroughly to eliminate any residue.
• The Bunsen burner was set up, and the flame was adjusted to the desired height.
• A sample was placed on the spatula, and the formula of the salt solution was recorded in Table 1.
• The spatula with the salt solution was exposed to the flame, and the resulting flame color was recorded in Table 1.
• The spatula was immersed in hydrochloric acid, rinsed with water, and then subjected to the flame again to burn off any remaining residue from the salt solution.
• This procedure was repeated for the remaining seven salt solutions and the unknown solution.
• All equipment was properly cleaned and stored at the end of the experiment.

Table 1: Flame Test Results

Table 2: Test of Unknown Solution

Results and Discussion

The data presented in Table 1 clearly demonstrate that each metal tested produces a distinct flame color during the flame test. This observation is consistent with the concept of each metal having a unique bright line spectra.

Table 2 illustrates how a flame test can be employed to identify metals in compounds. In this experiment, the light orange flame color identified the metal in the unknown solution as potassium nitrate (K(NO 3 )). These findings support the initial hypothesis that different metals emit different flame colors when exposed to a flame.

In conclusion, this lab experiment aimed to determine the characteristic flame colors of various metallic ions in a flame test and understand the underlying principles of fireworks. It has practical applications in identifying elements in space, aiding scientists in assessing the presence of oxygen on distant planets, and selecting suitable metals for fireworks to achieve specific colors.

The experiment involved burning salt samples and recording the resulting flame colors, confirming the hypothesis that each metal emits a distinct color when exposed to a flame. Furthermore, the experiment demonstrated that the flame color can be used to identify the metal in a compound by comparing it to previous data.

Future experiments could involve more advanced techniques, such as spectrometry, to determine the precise wavelengths of light emitted by each element during a flame test, enhancing the accuracy of element identification. Possible sources of error in this experiment include incomplete cleaning of the nichrome wire, potential interference from other light sources, and the presence of particles in the Bunsen burner.

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2.6: Flame test

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• Page ID 369380

• Muhammad Arif Malik
• Hampton University, Hampton, VA

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A flame test is a complex phenomenon that is not fully explained. In simple words, when a solution of metal salts, e.g., an aqueous solution of metal chlorides is injected into a flame, some of the metal ions may gain electrons and become neutral metal atoms. Electrons in the atom can be promoted from the ground state to a higher energy excited state by the strong heat of the flame. The excited electrons ultimately return to the ground state either in one go or in several steps by jumping to lower allowed energy states. When the excited electrons jump from higher to lower allowed energy states they emit electromagnetic radiation of a specific wavelength corresponding to the energy gap between the energy states. Some of these radiations may fall in the visible part of the electromagnetic radiation spectrum. The color we see is a combination of all the colors in the emission spectrum, as illustrated in Fig. 2.7.1.Figure \(\PageIndex{1}\).

The exact gap between the energy levels allowed for electrons varies from one metal to another metal. Therefore, different metals have different patterns of spectral lines in their emission spectrum, and if some of these spectral lines fall in the visible spectrum range, they impart different colors to the flame. For example, the ground-state electron configuration of the sodium atom is 1s 2 2s 2 2p 6 . When the sodium atom is in the hot flame some of the electrons can jump to any of the higher energy allowed stages, such as 3s, 3p, etc. The familiar intense yellow flame of sodium is a result of excited electrons jumping back from 3p 1 to ground state 3s 1 level.

Flame test procedure

Often metal chloride salts are used for the flame tests as they are water-soluble and easier to vaporize in flame from the solution. Metal chloride salts are first dissolved in water. Other metal salts are first treated with 6M \(\ce{HCl}\) to dissolve them as metal chlorides and then used for the flame test. An inert platinum wire is dipped in the test solution. Usually, the wire has a small loop a the end to make a film of the solution that evaporates in the flame. Air and fuel supply to the flame are adjusted to produce a non-luminous flame. The wire carrying the salt solution is touched on the outer edge of a flame somewhere in the middle of the vertical axis of the flame and the color imparted to the flame is observed. Nichrome wire is a cheaper alternative to platinum wire, though nichrome may slightly alter the flame color. A wooden splint or wooden cotton-tipped applicator are other cheaper alternatives. The wooden splint or cotton swab applicator is first dipped in deionized or distilled water overnight so that the cotton or wood may not burn when placed in a flame for a short time. The salt solution is then applied to the wooden splint end or to the cotton swab and exposed to the flame.

Wooden splint and cotton-tipped applicators are disposable, i.e., they are discarded after one flame test. Platinum wire can be reused after washing. The wire is dipped in 6M \(\ce{HCl}\) and then heated in a flame to red-hot. The process is repeated till the wire does not alter the color of the flame. Then it can be re-used. Nichrome wire can be washed the same way. However, an easier alternative is to cut out the loop of the wire and make a new loop on the fresh end portion. Then use the wire for the next flame test.

Figure \(\PageIndex{2}\) shows that flame tests tested using calcium chloride work equally well with nichrome wire, cotton-tipped applicator, and wooden splint. Figure \(\PageIndex{3}\) shows flam colors of some metal chloride salt solutions exposed to the flame on a cotton swab applicator.