Question

When heated in a flame, sodium salts produce a golden yellow color while potassium salts impart a lilac color to the flame. Explain why different colored flames are observed.

Answer 1

For example, a sodium ion in an unexcited state has the structure 1s22s22p6.

When you heat it, the electrons gain energy and can jump into any of the empty orbitals at higher levels - for example, into the 7s or 6p or 4d or whatever, depending on how much energy a particular electron happens to absorb from the flame.

Because the electrons are now at a higher and more energetically unstable level, they tend to fall back down to where they were before - but not necessarily all in one go.

An electron which had been excited from the 2p level to an orbital in the 7 level, for example, might jump back to the 2p level in one go. That would release a certain amount of energy which would be seen as light of a particular colour.

However, it might jump back in two (or more) stages. For example, first to the 5 level and then back to the 2 level.

Each of these jumps involves a specific amount of energy being released as light energy, and each corresponds to a particular colour.

As a result of all these jumps, a spectrum of coloured lines will be produced. The colour you see will be a combination of all these individual colours.

The exact sizes of the possible jumps in energy terms vary from one metal ion to another. That means that each different ion will have a different pattern of spectral lines, and so a different flame colour.