Question

By the axial overlapping of two p-orbitals of the same energy, a strong sigma bond is formed.
(A)- True
(B)- False
(C)- Ambiguous
(D)- None of these

Answer 1

The axial overlapping is the axis joining the nucleus of the two atoms forming the bond. Also, though the three p-orbitals are degenerate, they are directional in nature.

Complete step by step answer:
A sigma bond is formed by the overlapping of the atomic orbitals or the hybridised orbitals along the internuclear axis connecting the two atoms. The atomic orbitals can be s-, p- or d- orbital, where the s-orbital is non-directional due to being spherically symmetrical. So, the overlapping of the half-filled s-orbitals, they share their electron with the adjacent s-orbital along the line connecting the two atoms forming a covalent bond.
But in case of the p-orbitals, it has the electron-density distributed within the two lobes pointed in the direction of the three axes and a plane passing through the nucleus where probability of finding the electron is zero. Thus, the p-subshell having three orbitals each directed along the axes, having the same energy, that is, degenerate.

During the p-p overlapping along the internuclear axis, the half -filled ${{p}_{Z}}$ -orbitals of the two atoms undergo head-on overlap. This is thus the co-axial overlapping forming a sigma covalent bond.

As, the electron density on the bond axis is increased, due to maximum overlapping possible along the axis connecting the two atoms along the nucleus. It forms a very strong sigma bond.

Therefore, the axial overlapping of the two p-orbitals of the same energy forming a strong sigma bond is option (A)- true.

Note: The ${{p}_{X}}\,and\,{{p}_{Y}}$ orbitals show sidewise overlapping as they are present perpendicular to the internuclear axis, but parallel to the adjacent ${{p}_{X}}\,or\,{{p}_{Y}}$ orbital respectively, thus, forming the pi-bond.