Assume weak-field ligands give high spin, cyanide gives low spin, and take [Co(NH3)6]^3+ as low spin. Which complex has the highest spin-only magnetic moment: [Cr(H2O)6]^3+, [Mn(H2O)6]^2+, [Fe(CN)6]^4- or [Co(NH3)6]^3+?

JEE Main levelSingle correct optionDifficulty 2 of 3cc031

Assume weak-field ligands give high spin, cyanide gives low spin, and take $[Co (NH X_{3}) X_{6}] X^{3 +}$ as low spin. Which complex has the highest spin-only magnetic moment: $[Cr (H X_{2} O) X_{6}] X^{3 +}$ , $[Mn (H X_{2} O) X_{6}] X^{2 +}$ , $[Fe (CN) X_{6}] X^{4 -}$ or $[Co (NH X_{3}) X_{6}] X^{3 +}$ ?

Unpaired electrons: Mn(II) high spin

d^{5}

has 5, giving

35 = 5.92

BM. Cr(III)

d^{3}

has 3 (

3.87

BM). Fe(II) low spin

d^{6}

and Co(III) low spin

d^{6}

both have 0.