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In which one of the following species does the central atom have the type of hybridisation which is not the same as that present in the other three?
A
$PCl_5$
B
$SF_4$
C
$I_3^-$
D
$SbCl_5^{2-}$
Detailed Solution
Count σ bonds + lone pairs on the central atom.
$PCl_5$: 5 bond pairs + 0 lone pairs = 5, so $sp^3d$.
$SF_4$: 4 bond pairs + 1 lone pair = 5, so $sp^3d$.
$I_3^-$: the central I has 2 bond pairs + 3 lone pairs = 5, so $sp^3d$.
$SbCl_5^{2-}$: Sb has 5 valence electrons + 2 from the charge = 7; five are used in bonds, leaving one lone pair. 5 bond pairs + 1 lone pair = 6, so $sp^3d^2$.
Hence $SbCl_5^{2-}$ has a different hybridisation from the other three.
$PCl_5$: 5 bond pairs + 0 lone pairs = 5, so $sp^3d$.
$SF_4$: 4 bond pairs + 1 lone pair = 5, so $sp^3d$.
$I_3^-$: the central I has 2 bond pairs + 3 lone pairs = 5, so $sp^3d$.
$SbCl_5^{2-}$: Sb has 5 valence electrons + 2 from the charge = 7; five are used in bonds, leaving one lone pair. 5 bond pairs + 1 lone pair = 6, so $sp^3d^2$.
Hence $SbCl_5^{2-}$ has a different hybridisation from the other three.