SATHEE: Chemical Bonding - Result Question 14

Chemical Bonding - Result Question 14

####14. Among the species given below, the total number of diamagnetic species is

$H$ atom, $N O_{2}$ monomer, $O_{2}^{-}$ (superoxide), dimeric sulphur in vapour phase, $M n_{3} O_{4}, {(N H_{4})}_{2} [F e C l_{4}], {(N H_{4})}_{2} [N i C l_{4}]$ , $K_{2} M n O_{4}, K_{2} C r O_{4}$

(2018 Adv.)

Assertion and Reason

Read the following questions and answer as per the direction given below:

(a) Statement I is true; Statement II is true; Statement II is the correct explanation of Statement I

(b) Statement I is true; Statement II is true; Statement II is not the correct explanation of Statement I

(d) Statement I is incorrect; Statement II is correct

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Answer:

Correct Answer: 14. (1)

Solution:

Among the given species only $K_{2} C r O_{4}$ is diamagnetic as central metal atom $C r$ in it has $[A r] 3 d^{0}$ electronic configuration i.e., all paired electrons. The structure and oxidation state of central metal atom of this compound are as follows

Structure $K^{+} [\begin{array}{cc} \overset{O}{O} \overset{C r}{C r} O^{'} & O^{-} \end{array}]$ , Oxidation state $O^{6 +}$

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) $N O_{2}$ , i.e. $\overset{⊙}{O / P^{↘}} ↘_{O}$ in itself is an odd electron species.

(iii) $O_{2}^{-}$ (Superoxide) has one unpaired electron in $π *$ molecular orbital.

(iv) $S_{2}$ in vapour phase has $O_{2}$ like electronic configuration i.e., have 2 unpaired electrons in $π *$ molecular orbitals.

(v) $M n_{3} O_{4}$ has following structure

Thus, $M n$ is showing +2 and +4 oxidation states. The outermost electronic configuration of elemental $M n$ is $3 d^{5} 4 s^{2}$ . Hence, in both the above oxidation states it has unpaired electrons as

(vi) ${(N H_{4})}_{2} F e C l_{4}$ has $F e$ as central metal atom with +2 oxidation state. The electronic configuration of $F e^{2 +}$ in the complex is

(vii) ${(N H_{4})}_{2} N i C l_{4}$ has $N i$ as central metal atom with +2 oxidation state. The electronic configuration of $N i^{2 +}$ in the complex is