Question

Which of the following molecules possess V-shape ?
A. $O_3$
B. $N_3^-$
C. $CO_3^{2-}$
D. $NO_2^-$
E. $NO_3^-$
Choose the most appropriate answer from the options given below :

• A. A, D only
• B. A, B, D only
• C. C, D, E only
• D. C, E only

Hint:

"V-shape" or "bent" geometries usually arise from central atoms with $sp^2$ hybridization and one lone pair (bond angle $\sim 119^\circ$, e.g., $SO_2$, $O_3$, $NO_2^-$) or $sp^3$ hybridization with two lone pairs (bond angle $\sim 104.5^\circ$, e.g., $H_2O$, $H_2S$).

Answer 1

The Correct Option is A

Step 1: Concept:
The question asks us to identify which of the provided molecules or ions have a "V-shape" (often referred to as a "bent" or "angular" geometry). This requires using VSEPR (Valence Shell Electron Pair Repulsion) theory to determine molecular geometry.

Step 2: Key Formula or Approach:
For a central atom A, calculate the Steric Number (SN) = (Number of bonded atoms) + (Number of lone pairs).
- SN = 2 (0 lone pairs) $\rightarrow$ Linear
- SN = 3 (0 lone pairs) $\rightarrow$ Trigonal planar
- SN = 3 (1 lone pair) $\rightarrow$ Bent V-shape (angle $< 120^\circ$)
- SN = 4 (2 lone pairs) $\rightarrow$ Bent V-shape (angle $\approx 104.5^\circ$)

Step 3: Step-by-step Explanation:
Let's evaluate each species:

• A. $O_3$ (Ozone): The central oxygen atom is bonded to two other oxygen atoms and has one lone pair. SN = $2+1 = 3$. The electron geometry is trigonal planar, but the molecular geometry (ignoring the lone pair) is Bent (V-shape).

• B. $N_3^-$ (Azide ion): The central nitrogen is double-bonded to the two terminal nitrogens and has no lone pairs on the central atom. SN = $2+0 = 2$. The molecular geometry is Linear.

• C. $CO_3^{2-$ (Carbonate ion):} The central carbon is bonded to three oxygen atoms (one double bond, two single bonds theoretically, but resonance stabilized) and has no lone pairs. SN = $3+0 = 3$. The molecular geometry is Trigonal Planar.

• D. $NO_2^-$ (Nitrite ion): The central nitrogen is bonded to two oxygen atoms and carries one lone pair. SN = $2+1 = 3$. Similar to ozone, the molecular geometry is Bent (V-shape).

• E. $NO_3^-$ (Nitrate ion): The central nitrogen is bonded to three oxygen atoms and has no lone pairs (using its lone pair to form a coordinate bond/double bond structure). SN = $3+0 = 3$. The molecular geometry is Trigonal Planar.
Thus, only $O_3$ (A) and $NO_2^-$ (D) possess a V-shape.

Step 4: Final Answer:
Molecules A and D only, which corresponds to option (A).