Engineering Chemistry S Datta

VALENCY AND CHEMICAL BONDING 25
d 2 sp 3 or sp 3 d 2 hybridization
Electronic configuration of:
S-atom in ground state
3s
3p
3d
S-atom in excited state
Six unpaired
electrons
sp 3
d 2
hybridization
These sp 3 d 2 hybrid orbitals of one S-atom overlap with p-orbitals of six F-atoms to form SF 6
.
F
F
F
S
F
F
No. of
electron pairs
in outer shell
of the atom
F
Fig. 2.16 Octahedral structure of SF 6
molecule.
Table 2.3
Hybrid
Shape of
Bond angles
orbital
the molecule
Example
2 sp Linear 180° BeF 2
, C 2
H 2
3 sp 2 Trigonal planar 120° BF 3
, C 2
H 4
4 sp 3 Tetrahedral 109° 28′ CH 4
, SiF 4
4 dsp 2 Square planar
90°
90° 90°
90° [Ni (CN) 4
] 2– ,
5 dsp 3 Trigonal bipyramidal 120° and 90° PCl 5
,
90°
(NH 3
) 2
Cl 2
2–
or sp 3 d Fe(CO) 5
` 6 d 2 sp 3 Octahedral 90° SF 6
,
or sp 3 d 2 Co(NH 3
) 6
VSEPR Theory and Molecular Model
It is interesting to note that if the central atom in a molecule is surrounded only by
overlapped bonding orbital or orbitals containing shared pairs of electrons (Bond pairs, bp) in
the valence shell, the molecule then acquires a regular geometry. When the central atom
contains one or more lone pairs (lp) of electrons in the valence shell with bond pairs (bp) the