Why do salts of the following ions `Cu^(2+),Ba^(2+),Sr^(2+),Ca^(2+),Na^(o+)` and `K^(o+)` impart colour to the flame?

Explanation

This is due to the fact that the chlorides of these are volatile and at higher temperature they ionise giving respective cations. Since the energy of bunsen flame is constant, different elements are excited to different level due to difference in their ionisation energies. When these excited electrons return to their original energy level. they emit the same amount of energy absorbed during excitation in the form of electromagnetic radiation which appears in the visible region of the specturm, thereby imparting a characteristic colour to flame.