Question

According to MOT (Molecular Orbital Theory), the molecular orbitals are formed by mixing of atomic orbitals through LCAO (linear combination of atomic orbitals). The correct statement (s) about molecular orbitals is/are Statement (a) : bonding molecular orbitals are formed by addition of wave-functions of atomic orbitals of same phase Statement (b) : anti-bonding molecular orbitals do not take part in bond formation because they belong to inner shells Statement (d) : anti-bonding molecular orbitals provide stability to molecules while bonding molecular orbitals make the molecules unstable.

• A. statement a, d
• B. Statement a, b, c
• C. Statement a, b, d
• D. Statement a, b

Answer 1

Answer: (D)

Statement a, b

According to Molecular orbital theory,

Statement (a) : Bonding orbitals are formed by addition of wave function of atomic orbitals of same phase.

It is true

For, a bonding orbital

${\psi }_{MO}={\psi }_A+{\psi }_B$

For, anti bonding orbital

${\psi }_{MO}={\psi }_A-{\psi }_B$

Statement (b) : anti bonding molecular orbitals do not take put in bond formation because they belong to inner shells

It is also true

Statement (d) : anti-bonding molecular orbitals provide stability to molecules while bonding orbitals makes the molecules unstable.

This is a wrong statement

Energy of bonding orbitals is less than that of anti bonding orbitals due to attraction of both the nulei. Hence, bonding electrons will make the molecule stable and anti bonding electrons will make the unstable.