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Chemical Bonding and Molecular Structure

Multiple Choice Questions

581.

Which of the following is isoelectronic with CO₂?

NO₂
NO
N₂O
N₂O₄

582.

All bond angles are exactly equal to 109° 28' in:

methyl chloride
iodoform
chloroform
carbon tetrachloride

583.

The molecular shapes of SF₄, CF₄ and XeF₄ are

different with 1, 0 and 2 lone pairs of electrons on the central atom, respectively
different with 0, 1 and 2 lone pairs of electrons on the central atom, respectively
the same with 1, 1 and 1 lone pair of electrons on the central atoms, respectively
the same with 2, 0 and 1 lone pairs of electrons on the central atom, respectively

584.

Which one of the following does not have sp² hybridised carbon ?

Acetone
Acetic acid
Acetonitrile
Acetamide

585.

The bond order of N $_{2}^{+}$ is

586.
Among the following, the pair in which the two species are not isostructural, is

SiF₄ and SF₄

IO $_{3}^{-}$ and XeO₃

BH $_{4}^{-} and {NH}_{4}^{+}$

PF $_{6}^{-}$ and SF₆

SiF₄ and SF₄

SiF₄ and SF₄ are not isostructural because SiF₄ is tetrahedral due to sp³-hybridisation of Si.

₁₄Si = 1s², 2s², 2p⁶, 3s² 3p² (In ground state)

₁₄Si = 1s², 2s², 2p⁶, 3s¹ 3p³ (In excited state)

Hence, four equivalent sp³-hybrid orbitals are obtained and they are overlapped by four
p-orbitals of four fluorine atoms on their axes. Thus, it shows following structure:

While SF₄ is not tetrahedral but it is distorted tetrahedral because in it S is sp³d hybrid and has a lone pair of electron.

₁₆S = 1s², 2s² 2p⁶, 3s²3p $_{x}^{2} 3 p_{y}^{1} 3 p_{z}^{1}$ (In ground state)

= 1s², 2s² 2p⁶, $\underset{{sp}^{3} d hybridisation}{\underset{⏟}{3 s^{2} 3 p_{x}^{1} 3 p_{y}^{1} 3 p_{z}^{1}, 3 d_{xy}^{1}}}$ (In first excitation state)

Hence, sp³d hybrid orbitals are obtained. One orbital is already paired and rest four are overlapped with four p-orbitals of four fluorine atoms on their axes in trigonal bipyramidal form. This structure is distorted from trigonal bi-pyramidal to tetrahedral due to involvement of repulsion between lone pair and bond pair.