Molecules with a permanent dipole moment include which of the following?

(P) $\mathrm{HCN}$

(Q) ${\mathrm{O}}_3$

(R)${\mathrm{XeF}}_2$

$\mathrm{HCN}$is a polar, linear-shaped molecule having one link between the $\mathrm{H}$and $\mathrm{N}$atoms and one $\mathrm{C}$atom in the middle. There is a constant dipole moment in this chemical connection. Due to the presence of $\mathrm{N}$in $\mathrm{HCN}$, which is not physically linked to hydrogen atoms, dipole-dipole forces are present between the $\mathrm{HCN}$molecule's electron pair.

A resonance structure is created when a single and a double bond between the centre oxygen and the flanking oxygens swap locations. While the other oxygens share a negative charge between them, the centre oxygen has a single formal + charge. Ozone ${\mathrm{O}}_3$ therefore has a constant dipole moment.