Question

How bonding and antibonding orbital are formed according to lcao

Answer 1

Whenever atoms interact to form a bond, the atomic orbitals combine to form molecular orbitals.

During these transition from atomic to molecular orbitals, both bonding and antibonding orbitals are formed.

Consider an atom X. It combines with another atom A to form XA molecule.

consider valence shell.

Let the 's' atomic orbital of X have an energy of 100J.
let S orbital of A have energy 200J
When 1 each s orbitals from A and X combine, 2 molecular orbital with energy 100+200=300J will be formed.

But this is highly unstable as energy of molecular orbital is very high. So, bonding won't happen, as energy is too high.

So, energy is split between both of them.

one molecular orbit takes, say 50J energy. Other will have rest 250J energy.

Now, one orbital has lower energy, so, now, the atoms can interact to form bonds.

The orbital with lower energy, is called bonding orbital, and those with higher are called antibonding.


They are formed by interaction of energy between them. When one orbitals loses energy, by conservation of mass, other gains energy, so bonding and antibonding are formed.