Chemical Bonding and Molecular Structure - Result Question 118
####122. Among the following which one is not paramagnetic? [Atomic numbers : $Be=4$, $Ne=10, As=33, Cl=17]$
[1998]
(a) $Cr^{-}$
(b) $Be^{+}$
(c) $Ne^{+2}$
(d) $As^{+}$
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Solution:
- (a) Paramagnetic character is based upon presence of unpaired electron
$ \begin{aligned} & Cl^{-}=1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p_x^{2} 3 p_y^{2} 3 p_z^{2} \\ & Be^{+}=1 s^{2} 2 s^{1} \end{aligned} $
$ \begin{gathered} Ne^{2+}=1 s^{2} 2 s^{2} 2 p_x^{2} 2 p_y^{1} 2 p_z^{1} \\ As^{+}=1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 3 d^{10} \\ 4 s^{2} 4 p_x^{1} 4 p_y^{1} 4 p_z^{1} \end{gathered} $
Hence only $Cl^{-}$do not have unpaired electrons.
