Question

Fluorine molecules are formed by
A) The axial p-p orbital overlap
B) The sideways p-p orbital overlap
C) The s-s orbital overlap
D) The s-p orbital overlap

Answer 1

Fluorine molecule is bonded by strong sigma bond. This type of covalent bond is formed by the head-to-head overlap of bonding orbitals along the internuclear axis. This is known as axial overlap or head-on overlap. p-p overlapping takes place when two half-filled p-orbitals of the two atoms approach each other.

Complete answer:
Before going to explain this solution. We will go with each option.
(a) The axial p-p orbital overlap:
In fluorine $2{p_z}$ orbitals are partially filled they will overlap in head to head fashion. Hence strong sigma bonds will be formed. Fluorine electronic configuration is $1{s^2}2{s^2}2{p^5}$ . So the last electron will go in ${p_z}$ orbital.

(b) The sideways p-p orbital overlap-
This type of overlapping is possible in ${p_x}$ and ${p_y}$ orbital. These orbits undergo sideways overlapping and the ${p_z}$ orbital will undergo head to head overlapping. Fluorine molecules will not undergo sideways p-p orbital overlap.

The rest of the overlapping is not possible in fluorine molecule as we can see that fluorine molecule as $9$ atomic number so its electronic configuration will be like $1{s^2}2{s^2}2{p^5}$ . In fluorine, there is $2p$ partially filled orbital, so fluorine molecules come to each other to overlap and this overlapping of molecules will result in a covalent bond.
Hence, the correct option is (A).

Note:
The strength of a bond depends upon the extent of overlapping. As we can see that fluorine molecule has $2{p^5}$ partially-filled orbital, if we will consider this $p$ orbital as normal $2p$ orbital instead of $2{p_z}$ orbital then we will make mistake and will choose the wrong option.