The covalence of central atom is maximum in

Options

A. HCN
B. `NH_4^(+)`
C. `PCl_5`
D. `H_2O`

Answer

To determine which compound has the maximum covalence of the central atom among the given options (HCl, NH4+, PCl5, H2O), we will analyze the covalence of the central atom in each compound step by step.

### Step-by-Step Solution:

1. **Identify the Central Atom**:
- For each compound, we need to identify the central atom.
- **HCl**: The central atom is Cl (chlorine).
- **NH4+**: The central atom is N (nitrogen).
- **PCl5**: The central atom is P (phosphorus).
- **H2O**: The central atom is O (oxygen).

2. **Determine the Number of Bonds**:
- Next, we will determine how many bonds each central atom forms.
- **HCl**: Chlorine forms 1 bond with hydrogen.
- Covalence = 1
- **NH4+**: Nitrogen forms 4 bonds (one with each hydrogen).
- Covalence = 4
- **PCl5**: Phosphorus forms 5 bonds (one with each chlorine).
- Covalence = 5
- **H2O**: Oxygen forms 2 bonds (one with each hydrogen).
- Covalence = 2

3. **Compare the Covalence Values**:
- Now we will compare the covalence values we calculated:
- HCl: 1
- NH4+: 4
- PCl5: 5
- H2O: 2

4. **Identify the Maximum Covalence**:
- The maximum covalence among the values is 5, which corresponds to PCl5.

5. **Conclusion**:
- Therefore, the compound with the maximum covalence of the central atom is **PCl5**.

### Final Answer:
The covalence of the central atom is maximum in **PCl5**.