The calculated magnetic moments (spin only value) for species

$\mu=\sqrt{n(n+2)} B M$

$=\sqrt{4(4+2)} \mathrm{BM}$

$=\sqrt{24} \mathrm{BM} \Rightarrow 4.90 \mathrm{BM}$

(ii) $\left[\mathrm{Co}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]^{-3}$

µ = 0

(iii) $\mathrm{MnO}_{4}^{-2}$

$\mathrm{Mn}^{+6} \Rightarrow[\mathrm{Ar}] 3 \mathrm{~d}^{1} \quad \mu=\sqrt{\mathrm{n}(\mathrm{n}+2)} \mathrm{BM}$

$=\sqrt{1(1+2)} \mathrm{BM}$

$=\sqrt{3} \mathrm{BM} \Rightarrow 1.73 \mathrm{BM}$