Question

The magnetic moments of $Cr$ ($Z=24$), $Mn$ ($Z=25$) and $Fe$ ($Z=26$) are $x,y$ and $z$ respectively. Hence,

• A. $x=y=z$
• B. $x=z<y$
• C. $x<y<z$
• D. $x>y>z$

Answer 1

The correct option is D $x>y>z$

Electronic configuration of
$Fe\left(26\right)=1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{6}4s^2$

So, the number of unpaired electrons $n=4$

Electronic configuration of
$Cr\left(24\right)=1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{5}4s^1$

So, the number of unpaired electrons, $n=6$

Electronic configuration of
$Mn\left(25\right)=1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{5}4s^2$

So, the number of unpaired electrons, $n=5$

$\text{Magnetic moment}\left(\mu \right)=\sqrt{n(n+2)}\text{B.M.}$
Where, $n=$ number of unpaired electrons.
Greater the number of unpaired electrons, greater will be the magnetic moment.
Thus, the correct order is $x>y>z$.