Question

as the period number increases on the periodic table (moving from the top of the table to the bottom),
a. the atomic number decreases and the atomic mass increases.
b. the number of the energy level containing the valence electrons decreases
c. the number of the energy level containing the valence electrons increases
d. the atomic number increases and the atomic mass decreases

Explanation:

As we move down the periodic table (increase in period number), each new period corresponds to a new, higher - energy electron shell. The valence electrons occupy these shells, so the energy level of the valence electrons increases. Also, generally, as the period number increases, the atomic number and atomic mass increase due to the addition of protons, neutrons, and electrons.

Answer:

C. the number of the energy level containing the valence electrons increases