Question

what does the period number tell about the energy levels occupied by electrons in an atom?
a. the period number tells how many electrons are in the highest energy level of the atom.
b. the period number tells how many energy sublevels are occupied in the atom.
c. the period number tells how many electrons are in each sublevel of the atom.
d. the period number tells which is the highest energy level occupied by the electrons.

Explanation:

The period number in the periodic table corresponds to the principal quantum number (n) of the highest - occupied energy level of an atom's electrons. It indicates which energy level is the outermost or highest occupied one. For example, an element in period 3 has electrons in the third energy level as its highest - occupied level.

Answer:

D. The period number tells which is the highest energy level occupied by the electrons.