The trend likely shown in the graph is ionization energy, as it increases across a period and decreases down a group, consistent with patterns described for the periodic table's ionization energy behavior. The correct answer is option D.
The trend shown in the graph would likely be ionization energy because the information provided indicates that ionization energy generally increases across a period (from left to right) and decreases down a group (from the top to the bottom of the periodic table). The trend for electronegativity similarly increases across a period, but since we do not have the specifics of the graph, ionization energy is a probable answer considering the information given.
The trend for atomic mass steadily increases as you move down groups and across periods predominantly due to the increase in protons and neutrons. Atomic radius increases from top to bottom due to the addition of energy levels and generally decreases from left to right due to the increase in nuclear charge, which pulls the electron cloud closer.
Defending the choice of ionization energy, we can refer to the periodic trend which suggests that ionization energy typically increases as you move from the left-hand side to the right-hand side of a period on the periodic table. This is due to the valence electrons being held more tightly by the increasing nuclear charge, leading to a higher energy requirement to remove an electron. Down a group, ionization energy generally decreases because the valence electrons are further away from the nucleus and are thus less attracted to it, which means they can be removed with less energy.
Therefore, option D is correct.