Statement A is correct. Nitrogen in oxidation states from +1 to +4 tends to disproportionate in acidic medium. For example, 3HNO2→HNO3+H2O+2NO.
Statement B is incorrect. Nitrogen does not have d-orbitals in its valence shell, so it cannot form dπ−pπ multiple bonds. It forms pπ−pπ multiple bonds.
Statement C is incorrect. The N-N single bond is weaker than the P-P single bond due to high interelectronic repulsion between the non-bonding electrons, which arises from the small N-N bond length.
Statement D is incorrect. Density increases down the group in group 15. Nitrogen is a gas and has the lowest density in its group, while bismuth has the highest.
Statement E is correct. Nitrogen has only four valence orbitals (one 2s and three 2p orbitals) available for bonding. Therefore, its maximum covalency is restricted to four.
Thus, only statements A and E are correct.
Answer: A and E Only