Molecular orbital theory is based on the principle of linear combination of atomic orbitals (LCAO). According to LCAO, when respective atomic orbitals of the atoms interact, they undergo constructive interference as well as destructive interference giving two type of molecular orbitals, i.e., bonding molecular orbital and antibonding molecular orbital of electrons. 

Electrons in these orbitals are filled according to aufbau principle, Pauli's exclusion principle and Hund rule.

Molecular Orbital Theory (MOT) is based on the principle of Linear Combination of Atomic Orbitals (LCAO).

• When atomic orbitals of atoms combine, they undergo constructive interference (forming a bonding molecular orbital) and destructive interference (forming an antibonding molecular orbital).

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• Bonding molecular orbitals (BMO) have lower energy and are more stable, while antibonding molecular orbitals (AMO) have higher energy and are less stable.

• The number of molecular orbitals formed is always equal to the number of atomic orbitals that combine.

Electron filling rules:

1. Aufbau Principle → Orbitals are filled in increasing order of energy.

2. Pauli’s Exclusion Principle → Each orbital can have a maximum of two electrons with opposite spins.

3. Hund’s Rule of Maximum Multiplicity → Orbitals of the same energy are singly filled first before pairing occurs.

 Thus, molecular orbital theory explains the electronic configuration, stability, magnetic properties, and bond order of molecules more accurately than valence bond theory.