The metal ions that have the calculated spin only magnetic moment value of 4.9 B.M. are
A. $\mathrm{Cr}^{2+}$
B. $\mathrm{Fe}^{2+}$
C. $\mathrm{Fe}^{3+}$
D. $\mathrm{Co}^{2+}$
E. $\mathrm{Mn}^{3+}$
Choose the correct answer from the options given below

Question

Aicharya · Accepted Answer

Given magnetic moment $=4.9$ B.M.
We know M.M $=\sqrt{\mathrm{n}(\mathrm{n}+2)}$ B.M.
Where, $\mathrm{n} \rightarrow$ No. of unpaired $\mathrm{e}^{-}$
$4.9=\sqrt{\mathrm{n}(\mathrm{n}+2)}$
We get $\mathrm{n}=4$
(A) ${ }_{24} \mathrm{Cr}^{2+} \Rightarrow[\mathrm{Ar}] 3 \mathrm{~d}^4$ (4 unpaired e)
(B) ${ }_{26} \mathrm{Fe}^{2+} \Rightarrow[\mathrm{Ar}] 3 \mathrm{~d}^6$ (4 unpaired e)
(C) ${ }_{26} \mathrm{Fe}^{3+} \Rightarrow[\mathrm{Ar}] 3 \mathrm{~d}^5$ (5 unpaired e)
(D) ${ }_{27} \mathrm{Co}^{2+} \Rightarrow[\mathrm{Ar}] 3 \mathrm{~d}^7$ (3 unpaired $\mathrm{e}^{-}$)
(E) ${ }_{25} \mathrm{Mn}^{3+} \Rightarrow[\mathrm{Ar}] 3 \mathrm{~d}^4 \quad\left(4\right.$ unpaired $\left.\mathrm{e}^{-}\right)$

The metal ions that have the calculated spin only magnetic moment value of 4.9 B.M. are A.…

Solution