Which element in the periodic table has the highest first electron affinity (exothermic electron gain enthalpy)? (Hard)
Answer and explanation
Correct answer: B. Chlorine
- Step 1: Although Fluorine is more electronegative, its 2p subshell is very small and compact, causing strong inter-electronic repulsions that hinder incoming electrons. Step 2. Chlorine has a larger 3p subshell with less repulsion, giving Chlorine the highest first electron affinity in the periodic table (-349 kJ/mol vs -328 kJ/mol for F). Answer: Chlorine. Why not the others: Fluorine is lower due to compact 2p repulsion; Bromine has lower affinity due to larger atomic radius; Oxygen has lower electron affinity than sulfur for similar reasons.
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