When flame testing a chemical, how can you tell which ion is responsible fo the flame colour?

Question

Just the positive, just the negative, or a combination?
Please help!

Answer 1

the metal ions, non metals emit light in the ultraviolet and infra red wavelengths.

Answer 2

The colour is usually due to the metal, because energy jumps involving nonmetals are usually at higher energy and in the ultraviolet. This is because metals hold on less tightly to their outer electrons.

If more than one substance is contributing to the colour, you can sort them out by using a spectrometer to identify the separate wavelengths.