Which of the following has least covalent `P-H` bond ? .

Options

A. `PH_(3)`
B. `P_(2)H_(6)`
C. `P_(2)H_(4)`
D. `PH_(6)^(o+)`

Answer

To determine which of the given compounds has the least covalent P-H bond, we will analyze the options provided: PH₃, PH₄, PH₆, and PH₆⁺.

### Step-by-Step Solution:

1. **Understanding Covalent Bonds**:
- Covalent bonds are formed by the sharing of electrons between atoms. The nature of these bonds can vary based on the electronegativity of the atoms involved and the overall charge of the molecule.

2. **Analyzing the Compounds**:
- **PH₃ (Phosphine)**: This compound has three hydrogen atoms bonded to a phosphorus atom. It is a covalent compound.
- **PH₄ (Phosphorus Tetrahydride)**: This compound has four hydrogen atoms bonded to phosphorus. It is also covalent.
- **PH₆ (Phosphorus Hexahydride)**: This compound has six hydrogen atoms bonded to phosphorus, and it is covalent as well.
- **PH₆⁺ (Phosphorus Hexahydride Cation)**: This compound has a positive charge, indicating that it has lost an electron. The presence of a positive charge affects the electron distribution in the molecule.

3. **Impact of Charge on Covalent Bonds**:
- In PH₆⁺, the positive charge on phosphorus means it will attract electrons more strongly than in the neutral compounds. This results in a partial ionic character in the bond due to the attraction of electrons towards the positively charged phosphorus atom.

4. **Comparing Covalent Character**:
- Since PH₆⁺ has a positive charge, it will exhibit some ionic character in its P-H bonds, making these bonds less covalent compared to the other neutral compounds (PH₃, PH₄, and PH₆).
- Therefore, PH₆⁺ will have the least covalent P-H bond among the options.

5. **Conclusion**:
- The compound with the least covalent P-H bond is **PH₆⁺**.

### Final Answer:
**PH₆⁺ has the least covalent P-H bond.**