Question

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

the energy of an electron can never be changed

the energy of an electron can be varied by any amount

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

the energy of an electron can always be predicted with 100% accuracy

Answer 1

The answer is to be found within the question. One of the main idea in quantum theory is that energy is radiated and absorbed in quanta rather than being continuous.

Based on that info, what would you guess the answer to be?

Answer 2

quanta refers to discrete packets of energy.

Answer 3

so what is the answer

Answer 4

First you need to understand electrons reside in shells which correspond to particular energy levels. Electrons can move from one level to another and that involves a fixed exchange of energy. Thus we can change their energy.

An electron does not have a state that exists somewhere between two energy levels, it has to be one particular energy level depending on the transition so we say the energy is quantized as fixed amounts. However the exact energy of the electron cannot be determined (partly due to Heisenberg's uncertainty principle where understanding the position of the electron reduces accuracy on its momentum, and vice versa), only the energy involved in transition between levels can be determined.



You can think of energy levels like jumping between floors on a lift. You never want to have the lift stuck halfway up a floor. So electrons can only transition in given energy levels.