With respect to halogen, four statement are given below:

(P) The bond dissociation energies for halogens art in the order: ${\mathrm{I}}_2<{\mathrm{F}}_2<{\mathrm{Br}}_2<{\mathrm{Cl}}_2$

(Q) The only oxidation state is -1.

(R) The amount of energy required for the excitation of electrons to the first excited state decreases progressively as we move from F to I.

(S)  They form ${\mathrm{HX}}_2^{-}$ species in their aqueous solution (X= halogen)

The correct statement are :

The bond dissociation energy of halogens is given in order: ${\mathrm{I}}_2<{\mathrm{F}}_2<{\mathrm{Br}}_2<{\mathrm{Cl}}_2$​.

The bond dissociation energy decreases down the group, but fluorine shows remarkably small dissociation energy.

In halogens, there are two bonding pair and 3 nonbonding pairs. Because of the small size of fluorine, these non-bonding pairs come closer to each other and repel each other to a maximum extent which causes a decrease in bond strength.