Question

Which correctly summarizes the trend in electron affinity?
It tends to be very high for group 2.
It tends to be more negative across a period.
It tends to remain the same across periods.
It tends to be more negative down a group.

Answer 1

"It tends to be more negative across a period." — correct.

Why: electron affinity (EA) is the energy change when an atom gains an electron; more negative EA means more energy released and a stronger tendency to accept an electron. Across a period left→right nuclear charge increases and atomic size decreases, so added electrons are held more strongly and EA generally becomes more negative. Common exceptions: noble gases (very small or positive EA), the Group 2 elements (Be, Mg) and some Group 15 elements (e.g., N) deviate from the simple trend. Down a group EA generally becomes less negative (less exothermic) due to increased distance and shielding.