Question

One of the main ideas of the Quantum Theory is that:

Answer 1

The energy of an electron can be change only by set amounts.

The electrons in an energy level of an atom can only move to a higher or lower energy level only if it absorbs or emits a certain amount of energy. If the electron does not have enough energy to move to the next energy level then it will never move.

Answer 2

the energy of an electron can be changed by only set amounts