What happens when an atom is exposed to an energy source such as electricity?

Explanation:

When energy is supplied to an atom then its electron(s) absorb the energy and therefore, they tend to move from a lower energy level to higher energy level.

And, when this electron moves from higher energy level to lower energy level then excess of energy absorbed by it is released in the form of visible light or radiation.

Therefore, we can conclude that when an atom is exposed to an energy source such as electricity then its electrons move towards higher energy level generating light of visible color.