Why do electrons gain energy?

☁️My Answer☁️:

Atomic electrons lose / gain energy when transferring from one orbital to another and hence emitting / absorbing a photon. Free electrons (by which I mean electrons that are not part of an atom) lose or gain energy by scattering inelastic ally with atoms or molecules. In this case, energy is transferred to / from the atom or molecule from / to the electron in the form of kinetic energy

"the periodic table is arranged in order of atomic number."

elements make up everything, and they combine to make compounds.

the answer is c