Chemical Bonding And Molecular Structure Ques 93
93. Which of the following has $p _{\pi}-d _{\pi}$ bonding?
[2002]
(a) $NO_3^{-}$
(c) $BO_3^{3-}$
(b) $SO_3{ }^{2-}$
(d) $CO_3^{2-}$
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Answer:
Correct Answer:68. (b)
Solution:
(b) In $SO_3^{-2}$
$S$ is $s p^{3}$ hybridised, so
$ _{16} S=1 s^{2} 2 s^{2} 2 p^{6} \underbrace{3 s^{2} 3 p_x^{1} 3 p_y^{1} 3 p_z^{1}} _{s p^{3} \text{ hybridisation }} \underbrace{3 d _{x y}^{1}} _{\text{unhybridised}} $
In ‘S’ unhybridized $d$-orbital is present, which will be involved in $\pi$ bond formation with oxygen atom.
$ _8 O=1 s^{2} 2 s^{2} 2 p^{4} $
In oxygen two unpaired $p$-orbitals are present in these one is involved in $\sigma$ bond formation while the other is used in $\pi$ bond formation
Thus in $SO_3^{2-}$, p $\pi$ and $d \pi$ orbitals are involved for $p \pi-d \pi$ bonding.
BETA
