The number of species below that have two lone pairs of electrons in their central atom is _________. (Round off to the Nearest Integer).

SF₄, BF$$_4^ - $$, ClF₃, AsF₃, PCl₅, BrF₅, XeF₄, SF₆

AX is a covalent diatomic molecule where A and X are second row elements of periodic table. Based on Molecular orbital theory, the bond order of AX is 2.5. The total number of electrons in AX is __________. (Round off to the Nearest Integer).

Among the following, the number of halide(s) which is/are inert to hydrolysis is _________.

(A) BF₃

(B) SiCl₄

(C) PCl₅

(D) SF₆

The number of Cl = O bonds in perchloric acid is, "________".