$N{a_3}[Fe{F_6}]$ $\to $ $s{p^3}{d^2}$ hybridisation $\to $ $3$ unpaired electrons
$[Cr{({H_2}O)_6}]S{O_4}$ $\to $ ${d^2}s{p^3}$ hybridisation $\to $ $3$ unpaired electrons
${K_4}[Fe{(CN)_6}]$ $\to $ ${d^2}s{p^3}$ hybridisation $\to $ No unpaired electrons
Zero magnetic moment means all the electrons paired.
$\left[\mathrm{V}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+},\left[\mathrm{Cr}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+},\left[\mathrm{Fe}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+},\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+},\left[\mathrm{Cu}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$
[ આપેલ પરમાણુ ક્રમાંક : $\mathrm{V}=23, \mathrm{Cr}=24, \mathrm{Fe}=26, \mathrm{Ni}=28 \mathrm{Cu}=29$ ]
$($At. No. $Mo = 42, Pt = 78)$
$(I)\, [Ma_3b_2c]^{n \pm}\,\,\, (II)\, [M(AB)_3]^{n \pm}\,\,\, (III)\, [Ma_2b_2c_2]^{n \pm}$
$(I)\,\,\,-\,\,\,(II)\,\,\,-\,\,\,(III)$