IIT JEE Ch.5. BONDING AND MOLECULAR STRUCTURE -Core Points

JEE Syllabus

Orbital overlap and covalent bond;
Hybridisation involving s, p and d orbitals only;
Orbital energy diagrams for homonuclear diatomic species;
Hydrogen bond;
Polarity in molecules, dipole moment (qualitative aspects only);
VSEPR model and shapes of molecules (linear, angular, triangular, square planar, pyramidal, square pyramidal, trigonal bipyramidal, tetrahedral and octahedral).
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Exceptions to octet rule

Hydrogen molecule only 2 electrons make it stable.

Incomplete octet of central atom

LiCl
BeH2
BeCl2
BH3
BF3

LiCl 4 electrons around central Li-atom
BeCl2 4 electrons around central Be-atom
BF3 6 electrons around central B-atom

Expanded octet of the central atom


PF5 has ten around P
SF6 hs twelve around S
IF7 has fourteen electrons around I
H2SO4 12 electrons around sulphur atoms

Odd elctron molecules

Nitric oxide, NO
Nitrogen 7 shared electrons
Oxygen 8


Nitrogen dioxide, NO2(there is a coordinate bond)
Nitrogen 7
both oxygens 8


------------------
Exceptions to octet rule

Hydrogen molecule only 2 electrons make it stable.

Incomplete octet of central atom

LiCl
BeH2
BeCl2
BH3
BF3

LiCl 4 electrons around central Li-atom
BeCl2 4 electrons around central Be-atom
BF3 6 electrons around central B-atom

Expanded octet of the central atom


PF5 has ten around P
SF6 hs twelve around S
IF7 has fourteen electrons around I
H2SO4 12 electrons around sulphur atoms

Odd elctron molecules

Nitric oxide, NO
Nitrogen 7 shared electrons
Oxygen 8


Nitrogen dioxide, NO2(there is a coordinate bond)
Nitrogen 7
both oxygens 8



Hydrogen Bonding

The attractive force which binds hydrogen atom of one molecule with electronegative atom (F,O or N) of another molecule is known as hydrogen bond or hydrogen bonding.



VSEPR model and shapes of molecules
linear - 2 electron pairs
angular,
triangular,- 3 electron pairs
square planar,
pyramidal,
square pyramidal,
trigonal bipyramidal,
tetrahedral - 4 electron pairs
octahedral).

The relation between number of electron pairs around the central atom and shape of molecule to be filled