Chemistry Class 11 Chapter 4 Chemical Bonding and Molecular Structure | Page 4

Dipole moment: The product of the magnitude of the charge and the distance between the centres of positive and negative charge. It is a vector quantity and is represented by an arrow with its tail at the positive centre and head pointing towards a negative centre. Dipole moment( μ) = charge( Q) × distance of separation( r)

SIGMA BOND: A covalent bond formed due to the overlapping of orbitals of the two atoms along the line joining the two nuclei( orbital axis) is called sigma( σ) bond. For example, the bond formed due to s-s and s-p, p-p overlapping along the orbital axis are sigma bonds.

Pi- BOND: A covalent bond formed by the side wise overlapping of p- or d- orbitals of two atoms is called as pi( π) bond. For example, the bond formed due to the sideways overlapping of the two p- orbitals is a pi- bond.

HYDROGEN BOND: The bond between the hydrogen atom of one molecule and a more electro- negative element of same or another molecule is called as hydrogen bond.

HYBRIDIZATION: The process of mixing of the atomic orbitals to form new hybrid orbitals is called hybridization. All hybrid orbitals of a particular kind have equal energy, identical shapes and are symmetrically oriented in shape.

The hybrid orbitals are designed according to the type and the atomic orbitals merging together, e. g.,

Molecule Type Example

AX 2 E 1

AX 2 E 2

NO 2 −, SO 2, O 3, CCl 2

H 2 O, OF 2

2−, NO3

−, SO3

AX3E1

NH 3, PCl 3