Introduction

• Molecular orbital (MO) theory was developed by F. Hund and R.S. Mulliken in 1932. • The electrons in a molecule are present in the various molecular orbitals as the electrons of atoms are present in the various atomic orbitals. • The atomic orbitals of comparable energies and proper symmetry combine to form molecular orbitals. • An atomic orbital is monocentric while a molecular orbital is polycentric. • The number of molecular orbital formed is equal to the number of combining atomic orbitals. When two atomic orbitals combine, two molecular orbitals are formed, one bonding while the other is antibonding molecular orbital. • The bonding molecular orbital has lower energy and hence greater stability than the corresponding antibonding molecular orbital. • Just as the electron probability distribution around a nucleus in an atom is given by an atomic orbital, the electron probability distribution around a group of nuclei in a molecule is given by a molecular orbital. • The molecular orbitals like atomic orbitals are filled in accordance with the Aufbau principle obeying the Pauli’s exclusion principle and the Hund’s rule.

Pre-Requisites:

Covalent bond, polyatomic molecule , orbital

Activity:

Hybrids for example (animals, plants) are mixture of two or more individual types.

Real Life Question:

How do molecules form?

Key Words / FlashCards

Learning aids / Gadgets

Real life uses :

Hybridisation gives rise to new types or varieties.

Places to visit :

Zoo, garden, gym.

Practical examples around us

What you learn in Theory:

Different types of hybridization give different geometries of polyatomic molecules.

What you learn in Practice:

Hybridisation is intermixing.