Question

The strength of sigma bonds formed by the axial overlap of s- or p-orbitals of 2nd shell of participating atoms decreases as:

Answer 1

Hint: In the formation of any diatomic molecule, there is a minimum energy state while their orbitals undergo partial interpenetration that happens with two atoms coming near it. The partial merging of atomic orbitals leads to the overlapping of atomic orbitals which results in the pairing of electrons.

Complete step by step solution:
When atoms are involved in the overlapping of atomic orbitals, their overlap may be positive, negative or zero depending on the wave function of the orbital and also sign of the orbital.
Depending on the types overlapping of orbitals the covalent bonds are classified into two types of bonds,
(1) sigma bond ( $\sigma$ )
(2) pi bond ( $\pi$ )
sigma bond ( $\sigma$ ): the overlap of bonding orbitals along the internuclear axis by an end to end formation of the covalent bond.
s-s overlapping: this overlapping of two half-filled s-orbitals through the internuclear axis as shown below:

s-p overlapping: this overlapping of two half-filled s-orbital from one atom and p-orbital from another atom.

p-p overlapping: this overlapping of two half-filled p-orbitals through the internuclear axis as shown below:

From the above orbitals overlapping, p-orbitals overlap maximum than s-orbital becomes minimum. The strength of the sigma bond depends on its bond length.

Thus, The strength of sigma bonds formed by the axial overlap of s- or p-orbitals of 2^nd shell of participating atoms decreases as:
p-p>p-s>s-s.

Note: The overlap of 1-s orbitals of two H-atoms with the covalent bond formed by overlapping of two atomic orbitals from hydrogen molecules. In the case of polyatomic molecules, the bond formation depends on the geometry of molecules. This will be explained by valence bond theory as shape, the formation, and the directional properties of bonds in polyatomic molecules.