Question

The wave function of a molecular orbital formed by reinforcing of wave functions of ΨA and ΨB of atomic orbitals A and B is represented as

a) Φ= ΨA + ΨB

b) Φ= ΨA - ΨB

c) Φ= ΨA * ΨB

d) None of the above

Answer 1

An atomic orbital is an electron wave, the waves of the two atomic orbitals may be in phase

or out of phase. Suppose ΨA and ΨB represent the amplitude of the electron wave of the

atomic orbitals of the two atoms A and B.

Case 1: When the two waves are in phase so that they add up and amplitude of the wave is Φ= ΨA + ΨB

Case 2: when the two waves are out of phase, the waves are subtracted from each other

so that the amplitude of a new wave is Φ ´= ΨA– ΨB

The molecular orbitals formed by the additive effect of the atomic orbitals are called bonding molecular orbitals and the molecular orbitals formed by the subtractive effect of atomic is called antibonding molecular orbitals.

The probability of finding the electrons in the bonding molecular orbital increases whereas it decreases in the antibonding molecular orbital.

There is a nodal plane between the two nuclei of an antibonding molecular orbital i.e. a

plane on which electron density is zero.