Answer
a. \( \mathrm{Se} < \mathrm{S} \)
b. \( \mathrm{I} < \mathrm{Br} < \mathrm{F} < \mathrm{Cl} \)
Work Step by Step
a. The electron affinity generally decreases down the periodic table. Therefore, selenium (\( \mathrm{Se} \)) will have a lower electron affinity than sulfur (\( \mathrm{S} \)).
b. The electron affinity generally becomes more negative as we move from left to right across a period and from bottom to top within a group in the periodic table. Therefore, the order from least negative to most negative electron affinity is: \( \mathrm{I} < \mathrm{Br} < \mathrm{F} < \mathrm{Cl} \) (F is an exception).
