Question

Indicate the wrong statement according to $VBT$ .
A.A sigma bond has no free rotation about the internuclear axis.
B.P-orbitals always have only sidewise overlapping.
C.S-orbitals never form ${\text{pi - bonds}}$ .
D.There can be more than one sigma bond between two atoms.

Answer 1

Hint: In inorganic chemistry the valence bond theory was introduced for covalent compounds, it was invented to show the formation of covalent bonds. After some time hybridization was also introduced in VBT.

Complete step by step answer:
To explain the formation of covalent compounds a theory was by Heitler and London which was named Valence bond theory or VBT. Some corrections were done in this theory by adding the hybridization concept in VBT. Some postulates were described to understand the valence bond theory. The important postulates of the valence bond theory are as follows:
In VBT it was mentioned that the bond formation takes place by the overlapping of two half filled atomic orbitals. The electrons taking part in overlapping get combined and rest in the overlapping region of the atomic orbitals. And it was clear that due to overlapping the density increases because the overlapping region has double matter. It was described in VBT that the greater extent of overlapping results in strong bonding. On the basis of overlapping two types of bonds were mentioned: sigma bond ($\sigma {\text{ bond}}$ ) and pi bond ($\pi {\text{ bond}}$ ).
When the atomic orbitals overlap on the internuclear axis sigma bond formation takes place. And the sidewise overlapping of orbitals results in pi bond formation. So there can be only one sigma bond. Due to sidewise overlapping the rotation is restricted while the sigma bond is free to rotate. The sidewise overlapping also provides the double stability hence pi bonds are stronger than sigma bonds.

So, the correct answer is Option A,D .

Note:
The overlapping of atomic orbitals depend on their shapes. The s – orbitals are spherical in nature so they only form sigma bonds. The p-orbitals are pairs of two lobes attached oppositely to each other so these can form pi bonds if sidewise overlapping is done.