Which statement correctly summarizes the trend in electron affinity across the periodic table?

• A. Electron affinity generally becomes more negative (increases) from left to right across a period and less negative (decreases) from top to bottom within a group.
• B. Electron affinity generally becomes less negative (decreases) from left to right across a period and more negative (increases) from top to bottom within a group.
• C. Electron affinity remains constant across periods and groups.
• D. Electron affinity is highest for alkali metals and lowest for halogens.

Answer: (A)

Verified step by step guidance

1. Understand that electron affinity refers to the energy change when an atom gains an electron, typically measured in kJ/mol. A more negative value means the atom releases more energy upon gaining an electron, indicating a stronger attraction for the added electron.
2. Recall the general trend across a period (left to right) in the periodic table: atoms tend to have a higher nuclear charge with similar shielding, which increases their attraction for additional electrons, making electron affinity more negative.
3. Recall the general trend down a group (top to bottom): atoms have more electron shells, increasing the distance between the nucleus and the added electron and increasing electron shielding, which reduces the attraction for the added electron, making electron affinity less negative.
4. Compare the given statements with these trends: the correct summary should state that electron affinity becomes more negative (increases) from left to right across a period and less negative (decreases) from top to bottom within a group.
5. Eliminate incorrect options by checking if they contradict these trends, such as stating electron affinity remains constant or is highest for alkali metals, which is not consistent with the known periodic trends.