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Q.
Which of the following is diamagnetic?
Delhi UMET/DPMTDelhi UMET/DPMT 2003
Solution:
In diamagnetic species all the electrons are paired when we write configuration according to molecular orbital theory. Whereas a paramagnetic species has at least one unpaired electron.
(i) $O _{2}=(8+8=16)$
$=\sigma 1 s^{2}, \sigma^{*} 1 s^{2}, \sigma 2 s^{2},\sigma^{*} 2 s^{2}$, $\sigma 2 p_{z}^{2}, \pi 2 p_{x}^{2}, \pi 2 p_{y}^{2}, \pi^{*} 2 p_{x}^{1}, \pi^{*} 2 p_{y}^{1} $
$\because$ It has two unpaired electrons.
$\therefore $ It is paramagnetic.
(ii) $B_{2}=(5+5=10)$
$=\sigma 1 s^{2}, \sigma^{*} 1 s^{2}, \sigma 2 s^{2}, \sigma^{*} 2 s^{2}$, $\pi 2 p_{x}^{1}, \pi 2 p_{y}^{1} $
$\because$ It has two unpaired electrons.
$\therefore $ It is paramagnetic.
(iii) $N_{2}^{+}=(7+7-1=13)=$
$\sigma 1 s^{2}, \sigma^{*} 1 s^{2}, \sigma 2 s^{2}, \sigma^{*} 2 s, \pi 2 p_{x}^{2}, \pi p_{y}^{2}, \sigma p_{z}^{1}$
$ \because$ It has one unpaired electron.
$\therefore $ It is paramagnetic.