VSEPR THEORY

     This theory is based upon repulsions. It says that repulsion order is

 l.p.-l.p. > l.p.-b.p.>b.p.-b.p.

                                         VBT THEORY

• This theory is based upon overlapping of hybrid and pure orbitals.
• Hybridization = σ bonds + l.p.
• Size of all hybrid orbitals is same & all form σ bonds only except in benzyne.
• In sp³d³ the three d orbitals are d_xy, ,d_yz, d_xz
• In sp³d², d orbitals are d_z², d_x²_-y²
• σ bonds are stronger than π bonds.
• Attraction µstabilityµB.E µ 1/repulsion µ1/B.Lµ B.O.
• More no. of covalent bonds, more stability
• Order of Bond Strength is

             sp³-sp³< sp³-sp²< sp²-sp²< sp²-sp< sp-sp

• Size of hybrid orbital µ 1/s character µ BondStrength

• B.S.=> p-p > p-s > s-s

 Shapes of molecules using VBT and VSEPR

H-Bonds

• Shown by F, N & O. sometimes Cl

• Strength of H bond: H…F > H…O > H…N

Ion- Dipole attractions

Attraction between ion and dipole.

Van Der Waals forces

Forces of attraction and repulsion between constituents of a substance.

1.  Dispersion forces(nonpolar molecules)
2. Dipole- Dipole forces(polar molecules)
3. Dipole induced dipole forces(between one polar and other non polar molecule)

General points:

Boiling point µMolecular mass µH bonding µpolarity

Van Der Waals forces µmolecular mass

 the symbol µ represents "is proportional to"