An ion of a first-row transition metal has a spin-only magnetic moment of 4.90 BM. Which ion could it be?
Correct answer A. Fe²⁺
Explanation
μ = √(n(n + 2)) = 4.90 gives n = 4 unpaired electrons. Fe²⁺ (3d⁶) has 4 unpaired; Fe³⁺ has 5, Co²⁺ has 3 and Cu²⁺ has 1.
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