What do we mean when we say that electron energy level in atoms are quantized?

Question

what do we mean when we say that electron energy level in atoms are quantized? (under what circumstances can energy level transition occur?)

I am having trouble coming up with an answer.

What do you guys think?

I would really appreciate for your help!

Thank you in advance :)

Answer 1

Electrons that are tied to a nucleus have an energy, which dictates how far and where they can "orbit" around the nucleus.

If they have more energy, they change there orbit. Quantized means that they can't change there energy to any value, but have to move if fixed jumps.

One effect of this is that an electron in orbit can only absorb photons that will move it to one of its fixed energy levels.  Electrons not tied to a nucleus can have any energy level.

Answer 2

the energy is available only in discrete packets.

like steps on a ladder. energy can only exist on the steps not between.

this is why electrons don't collide into the nucleus of the atom.  the nucleus is between possible energy levels of the electrons.