Among B₂H₆, B₃N₃H₆, N₂O, N₂O₄, H₂S₂O₃ and H₂S₂O₈, the total number of molecules containing covalent bond between two atoms of the same kind is ...................

At 143 K, the reaction of XeF₄ with O₂F₂ produces a xenon compound Y. The total number of lone pair(s) of electrons present on the whole molecule of Y is .................

The total number of compounds having at least one bridging oxo group among the molecules given below is _________.

$${N_2}{O_3},{N_2}{O_5},$$ $${P_4}{O_6},{P_4}{O_7},$$ $${H_4}{P_2}{O_5},{H_5}{P_3}{O_{10}},$$ $${H_2}{S_2}{O_3},{H_2}{S_2}{O_5}$$