Explanation
The hybridization of central atom is as follows
SF4 → SP3d
XeF4→ SP3d2
SF6 → SP3d2
CF4→ SP3
The geometry of SF4 is trigonal bipyramidal, which has two types of F×F bond angles.
The angles around central atom H – M – H decreases from NH3 to SbH3 as,
Hydride
NH3
PH3
AsH3
SbH3
H – M – H angle
1070
920
910
900
This variation in bond angle can be explained on the basis of electronegativity of the central atom. Since nitrogen atom is highly electronegative. So in NH3 there is high electron density around the N – atom which cause greater repulsion between the electron pairs around the N – atom resulting in maximum bond angle. Since electronegativity decreases down the group, the electron density also decreases and consequently the repulsive interactions between the electron pairs also decreases there by decreasing the bond angle H – M – H.
∴ The order is NH3> PH3> AsH3> SbH3
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