BONDING

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Apply VSEPR to find their shapes...except SF₄, they are square planar(which means equal bond lengths). Due to lone pair in S, the bond angle decreases.

SF₄ -- see-saw shaped compound sp³d hybridisation so it has two kinds of S-F bonds axial and equatorial

XeF₄ Square planar sp²d

SiF₄ sp³ it's tetrahedral and not square planar

and BF₄^- also tetrahedral sp³

In square planar compounds hybridisation is sp²d so they involve participation of d-orbitals whereas in tetrahedral compounds hybridisation is sp³ and they do not have participation of d-orbitals..

square planar compounds hybridisation is not sp2d govind its dsp2 na??

SF₄--->sp³d

SiF₄---->sp³

Acc to VSEPR

(6+4)/2=5 and 1 lone pair => see saw shape....here the see saw shape is a bit hindered due to presence of lone pair electrons

XeF₄----> sp³d²

acc to VSEPR

(8+4)/2=6 and 2 lone pairs => square planar

BF₄- -----> sp³

Acc to VSEPR

(3+4+1)/2=4 and 0 lone pairs => tetrahedral shape

Each angle of tetrahedral = 109.5°

Each Angle of square planar= 90°

Angles of see saw shape = http://en.wikipedia.org/wiki/Sulfur_tetrafluoride