Spin only magnetic moment 2 .84 BM is given by: (Atomic Number of...

$\text{\mu} = \sqrt{\text{n}( \text{n} + 2 )} = 2.84 ⇒ \text{n} = 2$

electronic configuration of ${\text{Ni}}^{+ 2} = 1{\text{s}}^{2} 2{\text{s}}^{2} 2{\text{p}}^{6} 3{\text{s}}^{2} 3{\text{p}}^{6} 3{\text{d}}^{8}{\text{e}}^{-}$ having two unpaired electrons

electron configuration of $\text{T}{\text{i}}^{3 +} = 1{\text{s}}^{2} 2{\text{s}}^{2} 2{\text{p}}^{6} 3{\text{s}}^{2} 3{\text{p}}^{6} 3{\text{d}}^{1}$ only one unpaired electron

electron configuration of $\text{C}{\text{r}}^{2 +} = 1{\text{s}}^{2} 2{\text{s}}^{2} 2{\text{p}}^{6} 3{\text{s}}^{2} 3{\text{p}}^{6} 3{\text{d}}^{4}$ having four unpaired electrons

electron configuration of $\text{C}{\text{o}}^{+ 2} = 1{\text{s}}^{2} 2{\text{s}}^{2} 2{\text{p}}^{6} 3{\text{s}}^{2} 3{\text{p}}^{6} 3{\text{d}}^{7}$ having three unpaired electrons.