Final answer:
The first ionization energies increase as one moves from left to right across a period and from bottom to top within a group of the periodic table, which makes option a. (increase, increase) the correct answer.
Step-by-step explanation:
The correct answer to the question is a. increase, increase. As you move from left to right across a period on the periodic table, the number of protons in the nucleus increases, causing a stronger attraction between the nucleus and valence electrons. This results in an increase in effective nuclear charge and a decrease in atomic size, making it harder to remove an electron and thus the first ionization energy increases. Furthermore, as you go from the bottom to the top of a group, the valence electrons are closer to the nucleus and are more strongly attracted. Since the atomic size decreases up a group, the ionization energy also increases.