The designations s, p, d, f designate different types of electrons. a. Valence electrons. b. Different electron energy levels. c. Different electron orbitals within an energy level.

C

Explanation:

The electrons in an atom are specifically housed in locations that could be referred to as shells. These shells are the places where we can find an electron.

Now, within each shell, we have different energy levels in which these occupants electrons occupy. These energy levels have different energies and the amount of electrons they can take.

For example, the number of electrons S can take is 2 while that in which d can take is 10