Question

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 p$\pi$-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.

• A. (A), (B), (D) only
• B. (A), (C), (E) only
• C. (B), (D), (E) only
• D. (D) and (E) only

Answer 1

The Correct Option is D

Let's analyze each statement about group 15 elements to determine their correctness:

1. Statement (A): "Dinitrogen is a diatomic gas which acts like an inert gas at room temperature." 
   Nitrogen typically exists as a diatomic molecule (\(N_2\)). It is relatively inert under normal conditions due to the strong triple bond between the nitrogen atoms, making it stable and unreactive. Thus, Statement (A) is correct.
2. Statement (B): "The common oxidation states of these elements are −3, +3 and +5." 
   The group 15 elements indeed commonly show these oxidation states. For example, nitrogen can exhibit −3 (in ammonia), +3 (in nitrous acid), and +5 (in nitric acid). Statement (B) is correct.
3. Statement (C): "Nitrogen has unique ability to form p\(\pi\)-p\(\pi\) multiple bonds." 
   Nitrogen is capable of forming multiple bonds like \(\pi\)-bonds due to its small size and ability to undergo p\(\pi\)-p\(\pi\) overlap. This is correct, as seen in compounds like nitrogen gas (\(N_2\)). Statement (C) is correct.
4. Statement (D): "The stability of +5 oxidation states increases down the group." 
   The stability of the +5 oxidation state actually decreases down the group. Elements like bismuth prefer lower oxidation states due to the inert pair effect. Statement (D) is incorrect.
5. Statement (E): "Nitrogen shows a maximum covalency of 6." 
   Nitrogen, with its electron configuration of 1s² 2s² 2p³, can form a maximum of 4 covalent bonds (in compounds like ammonium ion, \(NH_4^+\)). Statement (E) is incorrect.

Thus, the incorrect statements are: (D) and (E).

Therefore, the correct answer is (D) and (E) only.

Answer 2

To identify the incorrect statements about group 15 elements, let's analyze each statement:

1. (A) Dinitrogen is a diatomic gas which acts like an inert gas at room temperature. 
   Dinitrogen (\( \text{N}_2 \)) is indeed a diatomic molecule and is relatively inert at room temperature. Therefore, statement (A) is correct.
2. (B) The common oxidation states of these elements are −3, +3 and +5. 
   Group 15 elements can exhibit oxidation states of -3, +3, and +5, among others, in their compounds. Therefore, statement (B) is correct.
3. (C) Nitrogen has unique ability to form pπ-pπ multiple bonds. 
   Nitrogen is known for forming pπ-pπ multiple bonds, such as in nitrogen-nitrogen (\( \text{N} \equiv \text{N} \)) and nitrogen-oxygen (\( \text{N} = \text{O} \)) bonds. Therefore, statement (C) is correct.
4. (D) The stability of +5 oxidation states increases down the group. 
   In reality, the stability of higher oxidation states, such as +5, decreases down the group due to the inert pair effect. Hence, statement (D) is incorrect.
5. (E) Nitrogen shows a maximum covalency of 6. 
   Nitrogen lacks available d-orbitals to expand its covalency beyond 4, thus it cannot show a covalency of 6. Therefore, statement (E) is incorrect.

Based on this analysis, the incorrect statements are (D) and (E).

The correct answer is: (D) and (E) only