c
Magnetic Moments (spin only)- \(\sqrt{n(n+2)}\)

where \(n=\) number of unpaired electron.

Number of unpaired \(e^{-} s\) and corresponding magnetic moments

\(1 \rightarrow 1.7\)

\(2 \rightarrow 2.8\)

\(3 \rightarrow 3.9\)

\(4 \rightarrow 4.9\)

\(5 \rightarrow 5.9\)

since \(B r^{-}\) is a weak feild ligand, so electrons in \(C o^{2+}\) will not pair up.

the complex has \(3\) unpaired electrons leaving it paramagnetic in nature.