Group 4A elements have much more negative electron affinities than their neighbors in groups 3A and 5A (see the figure).
Which of the following statements best explains this observation?
(i) The group 4A elements have much higher first ionization energies than their neighbors in groups 3A and 5A.
(ii) The addition of an electron to a group 4A element leads to a half-filled np3 outer electron configuration.
(iii) The group 4A elements have unusually large atomic radii.
(iv) The group 4A elements are easier to vaporize than are the group 3A and 5A elements.