Beginner Topic 624 of 1102 Inorganic Chemistry
Flame Tests
Alkali and alkaline earth ions give characteristic flame colors such as yellow for sodium and lilac for potassium.
In-depth explanation of Flame Tests
In a flame test, a metal salt is introduced into a non-luminous flame, and the colour observed reveals the metal. Heat excites electrons to higher energy levels, and when they fall back they emit light at wavelengths characteristic of each element. Each emitted photon has energy E = hc/lambda, so each colour corresponds to a specific wavelength. Sodium gives an intense yellow near 589 nm, lithium crimson, potassium lilac, calcium brick red, strontium red, barium apple green and copper blue-green. The same emissions give the colours of fireworks. Sodium's intense yellow can mask potassium's lilac, so cobalt glass is used to filter out the yellow light.
Going deeper: Flame Tests
Key ideas: Colors: Li crimson red, Na golden yellow (589 nm), K lilac, Rb red-violet, Cs blue, Ca brick red, Sr crimson, Ba apple green, Cu blue-green. Heat excites outer electrons, which emit visible photons as they fall back; E = h c divided by wavelength. Use a clean platinum or nichrome wire dipped in concentrated HCl to form volatile chlorides. View potassium through cobalt blue glass to filter out sodium.
Common mistakes and connections: Sodium contamination masks other colors since its yellow is intense. Students believe the color comes from the compound itself, whereas it is atomic emission from the metal. Li and Sr both look red, so confirm with other tests. Links to atomic spectra, energy quantization, fireworks and qualitative analysis of cations.
Visualization of Flame Tests
Characteristic emission wavelengths of metals in a flame; each colour corresponds to a photon energy E = hc/lambda from excited electrons falling back. The interactive lesson shows this as a live animation or chart.
Worked example and use case
A sodium salt in the flame gives an intense yellow that hides the lilac of potassium unless the yellow is filtered.
Frequently asked questions about Flame Tests
What is Flame Tests?
Alkali and alkaline earth ions give characteristic flame colors such as yellow for sodium and lilac for potassium.
Is Flame Tests a beginner, intermediate or advanced topic?
Flame Tests is a beginner topic in Inorganic Chemistry. It needs no earlier chemistry lessons and is a good starting point.
What should I learn before Flame Tests?
Study these earlier topics in Inorganic Chemistry first: Hydrogen Peroxide, Alkali Metals, Reaction of Alkali Metals with Water.
What comes after Flame Tests?
The next topics in Inorganic Chemistry are Sodium Chemistry and Sodium Hydroxide Production.
Can I practise Flame Tests with quizzes?
Yes. The interactive lesson includes a self-check question on Flame Tests, and the Inorganic Chemistry quiz draws on every topic in this area.
Where Flame Tests fits in Inorganic Chemistry
Flame Tests is topic 9 of 113 in Inorganic Chemistry.