b
Among given metals, \(\mathrm{Cr}\) has maximum \(\mathrm{IE}_2\)

because Second electron is removed from stable

configuration \(3 \mathrm{~d}^5\)

\(\mathrm{Cr}^{+}:[\mathrm{Ar}] 3 \mathrm{~d}^5 4 \mathrm{~s}^0\)

\(\therefore\) No of unpaired \(\mathrm{e}^{-}\)in \(\mathrm{Cr}^{+}\)is \(5, \mathrm{n}=5\)

\(\text { So, Magnetic moment } =\sqrt{\mathrm{n}(\mathrm{n}+2)} \text { B.M }\)

\(=\sqrt{5(5+2)}=5.92 \mathrm{BM} \approx 6\)