Chemical Bonding

## Fajan's Rule

Fajan's Rule states that a smaller cation with high charge density has more polarizing tendency than a larger cation with lesser charge density .

## Ionic Bond

An Ionic Bod is formed due to the complete transfer of electrons between interacting atoms . The ionic bonding can be explained using Born - Haber Cycle . The electronegativity difference between the interacting atoms should be more than 2 .

## Covalent Bond

A Covalent Bond is formed by sharing of electrons between two interacting atoms .
Covalent bonding gives rise to hard compounds , having high melting and boiling points .
Higher the number of covalent bonds , higher is the hardness of compound .

## Octet Rule

The Octet Rule states that the outermost shell of the interacting atoms should have a completely filled octet after formation of a bond .

## Bond Parameters

**Bond Length**

Bond Length is the distance between the nuclei of the interacting atoms . The smaller the Bond Length the greater is the Bond Strength .

**Bond Angle**

The Angle subtended by the bonds formed by peripheral atoms at the Central atom is called as Bond Angle .

**Bond Enthalpy**

The Energy needed to make or break a Bond is called as Bond Enthalpy . The Bond Enthalpy determines the Bond strength .

**Bond Order**

The number of bonds between two interacting atoms is called as Bond Order .

## Resonance

The formation of electron cloud density in double and triple bond compounds , due to the delocalization of pi electrons , is called as Resonance . Resonance makes a molecule more stable .

## Polar Character of Covalent Bond

When two atoms of different electronegativities form covalent bond , the more elctronegative atom pulls the electron density slightly towards itself . Thus polarity can be achieved in covalent compounds . The more the electronegativity difference , the more will be its polarity . An ionic Bond has more polarity than covalent bonds . A Polar Covalent Bond is an extreme case of Ionic Bond .

Dipole Moment = Q x R (Cm)
1 Debye = 3.33564 x 10-30 Cm

## Hybridization

The most important postulate of VBT states that the number of Bonds formed is same as the number of unpaired electrons in the central atom . This is achieved by Hybridization .

**sp3 Valency 4**

**sp2 Valency 3**

**sp Valency 2**

**sp3d Valency 5**

**sp3d2 Valency 6**

## Valence Shell Electron Pair Repulsion Theory

The Repulsion order is given by

Lone Pair - Lone Pair > Bond - Lone Pair > Bond - Bond

This theory is successful in explaining the geometry of Molecules .

(linear , trigonal planar , tetrahedral , square planar , square pyramidal , pyramidal , bipyramidal and octahedral structures to be studied [Coming Soon!])

## Molecular Orbital Theory

Molecular Orbitals are formed by the overlapping of two atomic orbitals of two different atoms . Bonding Molecular Orbitals have lower energy than the individual atomic orbitals , i.e. stable . The opposite is applicable for Anti-bonding Molecular Orbitals . The number of Molecular Orbitals is the same as the number of Atomic Orbitals .

For Bonding Molecular Orbitals ; b = A + B

For Anti-bonding Molecular Orbitals ; a = A - B

1) For every bonding molecular orbital , there is a corresponding anti-bonding molecular orbital .

2) Anti-Bonding Molecular Orbital will be opposite to Bonding Orbital .

3) Bonding Molecular Orbitals will participate in bonding .

4) Generally Anti-bonding Molecular Orbitals are empty .

5) Bonding and Anti-bonding Molecular orbitals can together hold 2 electrons .

## Dipole Moment

(Qualitative aspects only)
Dipole Moment = Q x R (Cm)

1 Debye = 3.33564 x 10-30 Cm