Explain why a bonding molecular orbital is of low energy while antibonding molecular orbital is of high energy?chemistry
We can answer this if we can define the types of orbitals.
Bonding molecular orbitals are formed when there is an in phase interaction thus making a constructive overlap which eventually forms an electron density located between the two nuclei. There is a low energy for that phenomenon to happen which apparently suggests the stability of bonding molecular orbitals.
Antibonding molecular orbital is located outside the area of two nuclei. This is due to the out of phase interaction of the orbitals thus creating less electron density and formation of nodal plane which apparently increase the energy. Since they are out of phase or destructive overlap, they tend to be repulsive and unstable which is related because antibonding molecular orbitals are of high energy.