With reference to protonic acids, which of the following statements is correct

Options

A. `PH_(3)` is more basic than `NH_(3)`
B. `PH_(3)` is less basic than `NH_(3)`
C. `PH_(3)` is equally basic as `NH_(3)`
D. `PH_(3)` is amphoteric while `NH_(3)` is basic.

Explanation

To determine which statement regarding protonic acids is correct, we need to analyze the properties of the compounds in question, namely NH3 (ammonia) and pH3 (phosphine).

### Step-by-Step Solution:

1. **Understanding Protonic Acids**:
- A protonic acid is defined as an acid that can donate protons (H+ ions) in solution. This means that when we consider the basicity of a substance, we are looking at its ability to accept protons.

2. **Analyzing NH3 (Ammonia)**:
- Ammonia (NH3) is known to be a strong base. This is due to the presence of a lone pair of electrons on the nitrogen atom, which allows it to readily accept a proton (H+).
- The small size of nitrogen allows the electron density of the lone pair to be concentrated, making NH3 very effective at attracting protons.

3. **Analyzing pH3 (Phosphine)**:
- Phosphine (pH3) is a hydride of phosphorus and is less basic compared to ammonia.
- As we move down the group in the periodic table from nitrogen to phosphorus, the size of the atoms increases. This increase in size leads to a decrease in ionization enthalpy and a diffusion of electron density over a larger area.
- Consequently, the ability of pH3 to attract protons is weaker than that of NH3.

4. **Comparing Basicity**:
- Given that NH3 is strongly basic due to its ability to donate its lone pair easily, while pH3 is weakly basic due to the larger size of phosphorus and the diffused electron density, we conclude that:
- **pH3 is less basic than NH3**.

5. **Conclusion**:
- Therefore, the correct statement is that "pH3 is less basic than that of NH3," which corresponds to option B.

### Final Answer:
The correct statement is: **pH3 is less basic than that of NH3 (Option B).**