Chemical Bonding - Result Question 115
14. Among the species given below, the total number of diamagnetic species is ______
$H$ atom, $NO _2$ monomer, $O _2^ {-}$ (superoxide), dimeric sulphur in vapour phase, $Mn _3 O _4,\left(NH _4\right) _2\left[FeCl _4\right],\left(NH _4\right) _2\left[NiCl _4\right]$, $K _2 MnO _4, K _2 CrO _4$
(2018 Adv.)
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Answer:
Correct Answer: 14. (1)
Solution:
- Among the given species only $K _2 CrO _4$ is diamagnetic as central metal atom $Cr$ in it has $[Ar] 3 d^{0}$ electronic configuration i.e., all paired electrons. The structure and oxidation state of central metal atom of this compound are as follows
Rest all the compounds are paramagnetic. Reasons for their paramagnetism are given below
(i) H-atom have $1 s^{1}$ electronic configuration, i.e. 1 unpaired electron.
(ii) $NO _2$, i.e. in itself is an odd electron species.
(iii) $O ^{-}_2 $ (Superoxide) has one unpaired electron in $\pi *$ molecular orbital.
(iv) $S _2$ in vapour phase has $O _2$ like electronic configuration i.e., have 2 unpaired electrons in $\pi *$ molecular orbitals.
(v) $Mn _3 O _4$ has following structure
Thus, $Mn$ is showing +2 and +4 oxidation states. The outermost electronic configuration of elemental $Mn$ is $3 d^{5} 4 s^{2}$. Hence, in both the above oxidation states it has unpaired electrons as
(vi) $\left(NH _4\right) _2 FeCl _4$ has $Fe$ as central metal atom with +2 oxidation state. The electronic configuration of $Fe^{2+}$ in the complex is
(vii) $\left(NH _4\right) _2 NiCl _4$ has $Ni$ as central metal atom with +2 oxidation state. The electronic configuration of $Ni^{2+}$ in the complex is
(viii) In $K _2 MnO _4$ central metal atom $Mn$ has +6 oxidation state with following structure
Electronic configuration of $Mn^{6+}$ is
BETA
