Final answer:
When an additional electron is added to an atom, its electron affinity usually becomes more negative, indicating energy release from the formation of an anion, particularly as you move left to right across the periodic table.
Step-by-step explanation:
When an additional electron is added to an atom, the electron affinity typically becomes more negative, reflecting that energy is released in the process. However, this trend can be complex as electron affinity can vary depending on the specific element and its electron configuration. Generally, as you move left to right across a period on the periodic table, electron affinity increases because the addition of electrons (forming an anion) is more favorable in lower energy orbitals closer to the nucleus. Conversely, as you move down a group, electron affinity becomes less negative due to the increase in atomic size and the relative decrease in nuclear attraction for the added electron. Thus, the correct answer in this context is d) It becomes negative, although it is worth mentioning that electron affinity can already be negative before the addition of an extra electron, as it is a measure of energy release.