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JEE Advanced levelSingle correct optionDifficulty 3 of 3cc086

A $d^{4}$ octahedral complex has $Δ_{o} = 21000 c m^{- 1}$ and pairing energy $P = 28000 c m^{- 1}$ . Assuming the single d-d band lies at $Δ_{o}$ , the spin-only moment and the absorption wavelength are

A4.90 BM and 357 nm
B2.83 BM and 357 nm
C4.90 BM and 476 nm
D2.83 BM and 476 nm

Answer: C

Since

Δ_{o}

is smaller than

P

, electrons occupy

t_{2 g}^{3} e_{g}^{1}

(high spin) with 4 unpaired, so

μ = 24 = 4.90 BM

. The wavelength is

λ = 1 0^{7} /21000 = 476 nm

. The value 357 nm would use

P

and is wrong.

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