Which of the following has the least covalent $P-H$ bond?

Which among the following is an electron-deficient compound?

Define the following: $(i)$ Bonding electron pair $(ii)$ Lone pair of electrons.

The potential energy $(y)$ curve for $H_2$ formation as a function of internuclear distance $(x)$ of the $H$ atoms is shown below.
The bond energy of $H_2$ is

The linear combination of atomic orbitals of two different atoms,each containing one electron,forms a ............ .

Provide a diagrammatic representation of the forces of attraction and repulsion during the formation of an $H_{2}$ molecule.