Question

A $\sigma$ bond may be formed by the overlap of 2 atomic orbitals of atoms A and B. If the bond is formed along the x-axis, which of the following overlaps is acceptable?

• A. $s$ orbital of A and $p_z$ orbital of B
• B. $p_x$ orbital of A and $p_y$ orbital of B
• C. $p_z$ orbital of A and $p_x$ orbital of B
• D. $p_x$ orbital of A and $s$ orbital of B

Answer 1

The correct option is D $p_x$ orbital of A and $s$ orbital of B

$p$-orbitals are directional in nature. So, only $p_x$ orbitals can take part in overlapping if bond is formed along $x$-axis.
However, $s$-orbital, being non-directional (spherical), overlaps in all the directions.
So, only $p_x$ and $s$ orbitals overlapping is favourable for the formation of sigma bond along x-axis.
($p_x$ of A and $s$ of B)