Concept:Across a period, atomic properties change due to increasing nuclear charge; down a group, increasing atomic size and shielding weaken the nucleus's hold on outer electrons.
Explanation:Ionization energy is the energy needed to remove an electron from a gaseous atom.
It increases from left to right across a period because nuclear charge increases and atomic radius decreases.
It decreases down a group because atomic radius increases and electrons are farther from the nucleus.
Electron affinity is the energy change when an atom gains an electron.
It also becomes more negative (increases in magnitude) across a period and becomes less negative down a group.
Atomic number increases both across a period and down a group, so it does not fit the trend "decreases down the group."
Metallic character decreases across a period and increases down a group, so it also does not fit.
Therefore, only ionization energy and electron affinity satisfy the stated trend.
Answer:B. ii and iv only