Question

Magnetic moment $2.83\, BM$ is given by which of the following ions? (At. no. $Ti =22, Cr =24, Mn =25, Ni =28$ )

• A. $Ti^{3+} $
• B. $Ni^{2+} $
• C. $Cr^{3+} $
• D. $Mn^{2+} $

Answer 1

Answer: (B)

Magnetic moment is given by $\mu = \sqrt {n(n+2)} $
Here, $n = $ number of unpaired electrons
$\Rightarrow 2.83=\sqrt {n(n+2)} $
$\Rightarrow (2.83)^2=n(n+2) $
$\Rightarrow 8.00=n^2+2n $
$\Rightarrow n^2+2n-8=0 $
$\Rightarrow n^2+4n-2n-8=0 $
$\Rightarrow (n+4)(n-2)=0 $
$\therefore n=2 [\because n \ne -4] $
Among the given ions:
Hence, $Ni^{2+} $ possesses a magnetic moment of $2.83\,BM$.