1) ICl has a linear shape due to sp3 hybridization of the iodine atom and the presence of three lone pairs on iodine, which causes distortion from the expected tetrahedral structure. 2) ClF3 has a slightly bent T-shape due to sp3d hybridization of the chlorine atom and two lone pairs, which distorts the trigonal bipyramidal structure. 3) IF5 has a square pyramidal shape due to one lone pair on the iodine atom, which distorts the octahedral structure expected for an sp3d2 hybridized central atom with five bonds and one lone pair.

1. Structure and shape of ICl:-
In AB type molecules A halogen atom is less electronegative than B halogen atom. The Lewis structure of AB
Molecule, shows that the central atom A (central atom is that which is less electronegative) is
surrounded by one σ- bonding electron pair and three lone pairs of electrons. i.e σ-bps+lps=1+3=4.
The central atom A is sp3 hybridized in AB molecule.
Example :- ICl molecule – sp3 hybridization by I-atom.
5s2 5px2 5py2 5pz1 (I atom-Gd state) sp3 hybridization (sp3)2(sp3)2(sp3)1 [Four sp3 hybrid orbitals three of
which contain a lone pair of electrons while the fourth hybride orbital is singly- filled].
This singly-filled sp3 hybrid orbital makes a head-to-head (linear) overlap with the singly- filled 3px orbital on
Cl-atom and forms one sp3 (I)- px(Cl) σ-bond.
xx ..
xxAx . B :
xx ..

2.  The spatial arrangement of the four electron pairs (bp=1 and lps=3) round 1 atom is
tetrahedral, due to the presence of three lone pair of electrons in three sp3 hybrid orbitals, the
shape of ICl molecule gets distorted and becomes linear.
 A-B bond lengths in AB type interhalogen molecules are as : ICl=2.321 A°

3. Structure of AB3 molecule :-
 AB3 molecule shows that the central atom A is surrounded by three σ-
bonding electron pairs and two lone pairs of electrons.[σ-bps+ lps=3=2=5]
 the central atom, A is sp3d hybridised in AB3 molecule
Structure and shape of ClF3
Cl atom is the central atom which undergoes sp3d hybridisation
B
B-A-B
….

4.  each of the three singly-filled sp3d hybrid orbitals makes a head-to-head(linear) overlap with the
singly filled 2p orbital on each F atom and forms sp3d(Cl)-p(F) σ bond as shown in fig 20.3
 The spatial arrangement of five electron pairs (bp=3 and lps=2) round Cl atom is trigonal
bipyramidal, due to the presence of two lone pairs of electrons, the shape of ICl molecule gets
distorted and becomes slightly bent T-shape, and the repulsion between the two lone pairs of
electrons reduces FaClFb bond angle from 90o to 87.5o.
 both Fa-Cl bond lengths are equal (=1.70 Ao) while Cl-Fb bond length is 1.60Ao

5.  The two lone pairs of electrons can occupy any of the three positions of the five positions of the
trigonal bipyramid and thus give three different structures a), b) and c) to ClF3 moleculeas shown
if fig 20.4
 the most stable of these 3 structures is that in which the lps occupy the basal positions of the
trigonal bipyramid

6. Structure and shape of ICl3 molecule:
 ICl3 in the solid state is dimeric with a chlorine-bridged structure shown in fig
 The dimer, (ICl3)2 is formed by joining two T-shaped IC3 molecules and is flat
Each I-atom is sp3d hybridised and is bonded to two bridging Cl-atoms and two terminal Cl-atoms.
Each I-atom has 2 lone pairs of electrons due to which(ICl3)2 molecule does not have the
expected regular trigonal bipyramidal but has a square planar shape

7. Structure and shape of AB5 type molecule:
 the central atom A is surrounded by five σ-bonding electron pairs and one lone pair of electrons, σ-
bps+lps=5+1=6
The central atom A is sp3d2 hybridised in AB5 molecule
Structure of IF5 molecule:
 The central atom which undergoes sp3d2 hybridisation

8.  In this case (lp-bp)repulsion is minimum
 each of the five singly-filled sp3d2 hybrid orbitals makes a head-to-head(linear) overlap with the
singly filled 2p orbital on each F atom and forms sp3d2(I)-p(F) σ-bond
 The spatial arrangement of six electron pairs (bp=5 and lps=1) round I atom is octahedral, due to
the presence of one lone pairs of electrons in the axial hybrid orbital, the shape of IF5 molecule
gets distorted and becomes square pyramidal
 Burbank and James has shown that the basal F-atoms(Fb)
are slightly displaced upwards from the base of the square
pyramid shown in fig 20.7
 FaIFb bond angle is 81.9o
I-Fa bond length (1.73Ao) is shorter than the I-Fb bond length
(1.87Ao)

9. Structure and shape of IF7 molecule:
 the central I atom is surrounded by seven σ-bonding electron pairs and no lone pair of
electrons(bps+lps=7+0=7)
 I atom is sp3d3 hybridised in this molecule
 the seven hybrid orbitals is singly-filled with electrons. Each singly-filled 2px orbital makes a head-
to-head(linear) overlap with the singly filled 2px orbital on F atom and forms seven I-F σ-bonds
 IF7 molecule has pentagonal bipyramidal shape which has two axial I-Fa bonds and five basal I-Fb
bonds.

10.  the angle between two I-Fa bonds is equal to 180o.
 Fa-I-Fb=90o, Fb-I-Fb=72o and
Fa-I-Fa=180o.
 both I-Fa bond lengths which are equal
to each other are greater than both
I-Fb bond lengths which are again equal
to each other