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Jump to one of the following atomic and electronic structure parts:   Choose One Introduction to Atomic Structure Part 1- Atomic Spectra Part 2- Quizzes

When heated, some elements emit visible light. I can take compounds made from these elements, put them in the flame of a burner, and then examine the flame color. One way to do this is to use wooden splints dipped in each compound. The splints need to be soaked for hours in distilled water. Since the wood becomes saturated with water, the splint does not readily burn and so does not contribute to the flame color (taken from Flinn publication #?). This procedure is also nice because the compound generally sticks quite well to the wet splint.

However, if I put sodium chloride into a flame, how do I know what the resultant color is due to? Sodium ion or chloride ion? I'm going to state that it's due to the sodium ion but you shouldn't necessarily believe me without some data, right? Here are four sodium compounds so you can judge for yourself-

sodium chloride	sodium iodide	sodium bromide	sodium nitrate
NaCl	NaI	NaBr	NaNO3

If the anion had anything to do with the flame color then I might expect to see some kind of major variation among the three halides and the nitrate compound. Since there is no major color variation, it's reasonable to point your finger at sodium ion. The heat from the flame excites electrons in sodium ionss. These excited electrons eventually drop back to their ground state and emit light whose wavelength falls in the visible yellow area of the electromagnetic spectrum.

How about some more colors?

red	scarlet	orangish	emerald green	violet
lithium carbonate	strontium nitrate	calcium chloride	copper(II) sulfate	potassium chloride
Li2CO3	Sr(NO3)2	CaCl2	CuSO4	KCl