Identify the incorrect statements about group 15 elements :

(A) Dinitrogen is a diatomic gas which acts like an inert gas at room temperature.

(B) The common oxidation states of these elements are $-3,+3$ and +5.

(C) Nitrogen has unique ability to form $\mathrm{p} \pi-\mathrm{p} \pi$ multiple bonds.

(D) The stability of +5 oxidation states increases down the group.

(E) Nitrogen shows a maximum covalency of 6.

Choose the correct answer from the options given below :

<p>Let's analyze each statement step by step to identify the incorrect ones:</p> <p>(A) Dinitrogen is a diatomic gas which acts like an inert gas at room temperature.</p> <p>This statement is generally correct. Dinitrogen ($N_2$) is indeed a diatomic gas and is very inert at room temperature due to the strong triple bond between the nitrogen atoms.</p> <p>(B) The common oxidation states of these elements are $-3,+3$ and +5.</p> <p>This statement is also correct. The group 15 elements commonly exhibit oxidation states of $-3$ (in nitrides), $+3$ (as in $\mathrm{NH}_3$), and +5 (as in $\mathrm{HNO_3}$).</p> <p>(C) Nitrogen has unique ability to form $\mathrm{p}\pi-\mathrm{p}\pi$ multiple bonds.</p> <p>This statement is correct. Nitrogen has a unique ability to form $p\pi-p\pi$ multiple bonds, which is why it can form a triple bond ($N_2$).</p> <p>(D) The stability of +5 oxidation states increases down the group.</p> <p>This statement is incorrect. The stability of +5 oxidation states actually decreases down the group due to the effect of inert pair effect. For example, bismuth in +5 state is less stable than nitrogen in +5 state.</p> <p>(E) Nitrogen shows a maximum covalency of 6.</p> <p>This statement is incorrect. Nitrogen can exhibit a maximum covalency of 4 (as in $\mathrm{NH_4^+}$). It cannot expand its octet to show a covalency of 6.</p> <p>Based on the above analysis, the incorrect statements are (D) and (E). Therefore, the correct answer is:</p> <p>Option B: (D) and (E) only</p>