Which of the following statement is incorrect?

Options

A. Ozone is violet-black in solid state
B. Ozone is diamagnetic gas
C. `NOCl and ONO^(-)` are isoelectronic
D. Ozone molecule is bent

Answer

To determine which statement is incorrect, we will analyze each option provided in the question step by step.

### Step 1: Analyze the statements
1. **Statement 1**: Ozone is violet-black in solid state.
2. **Statement 2**: Ozone is a diamagnetic gas.
3. **Statement 3**: NOCl and ONO⁻ are isoelectronic.
4. **Statement 4**: The ozone molecule is bent.

### Step 2: Evaluate Statement 1
- Ozone (O₃) in its solid state does appear violet-black. This statement is **correct**.

### Step 3: Evaluate Statement 2
- Ozone is a gas at room temperature and is indeed diamagnetic, meaning it has no unpaired electrons. This can be confirmed by drawing the molecular orbital diagram of ozone, where all electrons are paired. This statement is **correct**.

### Step 4: Evaluate Statement 3
- To determine if NOCl and ONO⁻ are isoelectronic, we need to count the total number of electrons in each species.
- **NOCl**: Nitrogen (N) has 7 electrons, Oxygen (O) has 8 electrons, and Chlorine (Cl) has 17 electrons. Therefore, NOCl has a total of 7 + 8 + 17 = 32 electrons.
- **ONO⁻**: The neutral oxygen (O) has 8 electrons, and the anion (O⁻) has 9 electrons. Therefore, ONO⁻ has a total of 8 + 9 + 8 = 25 electrons.

Since NOCl has 32 electrons and ONO⁻ has 25 electrons, they are not isoelectronic. This statement is **incorrect**.

### Step 5: Evaluate Statement 4
- The structure of ozone is indeed bent due to the presence of a lone pair of electrons on the central oxygen atom. This leads to a V-shaped molecular geometry. This statement is **correct**.

### Conclusion
The incorrect statement among the options is **Statement 3**: NOCl and ONO⁻ are isoelectronic.