Chemistry help!?

[Kod]

ok, so i have chemistry class, and we did this experiment were we had, these IONS, and Burned them, and they all had a different color flame.
IONS:
Sodium+
Potassium+
Calcium 2+
Strontium 2+
Lithium+
Copper 2+

then we had to anwser some questions but there were two of them were noone knew the anwsers for them, and so we are all stuck. The questions were:

1. Explain how colors are produced by the flame test. Include the terms " ground state" "exited state" and photon in your explanation.

2. Why did each metal have a different color flame? What dose this have to do with electrons?

So my question is. what are the anwsers to those questoins anyone know? Because ive been stuck for ours readint in the book they gave us at school and still nothing. Please someone help me!