Question

The calculated spin only magnetic moments of $\left[ Cr \left( NH _{3}\right)_{6}\right]^{3+}$ and $\left[ CuF _{6}\right]^{3-}$ in BM, respectively, are (Atomic number of $Cr$ and $Cu$ are $24$ and $29$ , respectively)

• A. 3.87 and 2.84
• B. 4.90 and 1.73
• C. 3.87 and 1.73
• D. 4.90 and 2.84

Answer 1

Answer: (A)

$\left[ Cr \left( NH _{3}\right)_{6}\right]^{3+}$ has $d ^{3}$ configuration, so as per $CFT$,
$N =3$ and $\mu=\sqrt{3(3+2)}=3.87 \,BM$
$\left[ CuF _{6}\right]^{3-}$, has $d ^{8}$ configuration and weak field ligand.
So $N =2$ and $\mu=\sqrt{2(2+2)}=2.84\, BM$