Nitrogen due to small size is able to show pπ-pπ lateral overlap forming N ≡ N, rest elements due to bigger size are not able to show pπ-pπ lateral overlap.

Only nitrates of heavy metals and lithium decompose on heating to produce NO₂.

Structure of hypophosphorous acid

Two H-atoms are attached to P atom.

CO₂ is oxide of non-metal. Both N₂O and NO₂ are also oxide of non-metal. They form acids on dissolution in water. In this way CO₂ resembles N₂O and NO₂. Option(d) is the answer.

We know that empirical formula of hypophosphrus acid is H₃PO₂. In this only one ionisable hydrogen atom is present i.e. it is monobasic. Therefore option (a) is correct structural formula of it.

As comparedto nitrogen, oxygen is more electronegative and more reactive because as we go from left to right in a group electronegativity in creases and reactivity decreases. So, nitrogen should be more reactive than oxygen but in nitrogen p-orbitals are exactly half filled which make it stable and less reactive as compared to oxygen.

H₃PO₂ is named as hypophosphorous acid. It is monobasic as it contains only one P – OH bond, its basicity is one.

N₂ molecule contains triple bond between N atoms having very high dissociation energy (946 kJ mol^–1)due to which it is relatively inactive.

HF (Hydrofluoric acid or Hydrogen flouride) is the acid which cannot be kept in glass because it reacts with glass

6HF + SiO₂ → H₂SiF₆ + 2H₂O.