Which of the following best describes the trend in electron affinity (EA) as you move down a group in the periodic table?

• A. Electron affinity fluctuates unpredictably down a group.
• B. Electron affinity remains constant down a group.
• C. Electron affinity generally decreases down a group.
• D. Electron affinity generally increases down a group.

Answer: (C)

Verified step by step guidance

1. Understand that electron affinity (EA) is the energy change when an atom gains an electron, typically releasing energy (exothermic).
2. Recall that as you move down a group in the periodic table, atoms have more electron shells, increasing the distance between the nucleus and the added electron.
3. Recognize that increased distance and electron shielding reduce the nucleus's effective attraction for the added electron, making the electron affinity less negative (less energy released).
4. Therefore, electron affinity generally decreases (becomes less exothermic) as you move down a group because the added electron is less strongly attracted.
5. Conclude that the best description of the trend is: Electron affinity generally decreases down a group.