# Which one of the following species doesn't have a magnetic

Question:

Which one of the following species doesn't have a magnetic moment of 1.73 BM, (spin only value) ?

1. $\mathrm{O}_{2}^{+}$

2. $\mathrm{CuI}$

3. $\left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\right] \mathrm{Cl}_{2}$

4. $\mathrm{O}_{2}^{-}$

Correct Option: , 2

Solution:

Species must not contain single unpaired

(1) $\mathrm{O}_{2}^{+} \rightarrow \sigma_{1 \mathrm{~s}}^{2}<\sigma_{1 \mathrm{~s}}^{* 2}<\sigma_{2 \mathrm{~s}}^{2}<\sigma_{2 \mathrm{~s}}^{* 2}<\sigma_{2 \mathrm{pz}}^{2}<\pi_{2 \mathrm{px}}^{2}=\pi_{2 \mathrm{py}}^{2}<\pi_{2 \mathrm{px}}^{* 1}=\pi_{2 \mathrm{py}}^{*}$

unpaired $\mathrm{e}^{-}=1 \therefore \mu=1.73 \mathrm{BM}$

(1) $\mathrm{Cu}^{+} \mathrm{I}^{-} \mathrm{Cu}^{+} \rightarrow[\mathrm{Ar}] 3 \mathrm{~d}^{10} \therefore$ unpaired $\mathrm{e}^{-}=0$

$\mathrm{I}^{-} \rightarrow[\mathrm{Xe}] \therefore$ unpaired $\mathrm{e}^{-}=0$

therefore $\mu=0$

3. $\left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\right] \mathrm{Cl}_{2}$

$\mathrm{Cu} \rightarrow[\mathrm{A}] 3 \mathrm{~d}^{3} \therefore$ unpaired $=1 \therefore \mu=1.73 \mathrm{BM}$

4. $\mathrm{O}_{2}^{-} \rightarrow \mathrm{d}$

$\sigma_{1 \mathrm{~s}}^{2}<\sigma_{1 \mathrm{~s}}^{* 2}<\sigma_{2 \mathrm{~s}}^{2}<\sigma_{2 \mathrm{~s}}^{* 2}<\sigma_{2 \mathrm{px}}^{2}<\pi_{2 \mathrm{px}}^{2}=\pi_{2 \mathrm{py}}^{2}<\pi_{2 \mathrm{px}}^{* 1}=\pi_{2 \mathrm{py}}^{*}$

$\left(11 \mathrm{e}^{-}\right)$

$\therefore$ unpaired $\therefore \mu=1.73 \mathrm{BM}$