For which element would `XH_(3)` be a stable species:

Options

A. C
B. Si
C. P
D. S

Explanation

To determine which element would form a stable species of the type \( XH_3 \), we will analyze the electronic configurations of the elements in the p-block and apply the octet rule.

### Step-by-Step Solution:

1. **Identify the Elements**: The elements we will consider are Carbon (C), Silicon (Si), Phosphorus (P), and Sulfur (S). These elements belong to Group 14, 14, 15, and 16 of the periodic table, respectively.

2. **Write the Electronic Configurations**:
- **Carbon (C)**: Atomic number 6
- Electronic configuration: \( 1s^2 2s^2 2p^2 \)
- **Silicon (Si)**: Atomic number 14
- Electronic configuration: \( 1s^2 2s^2 2p^6 3s^2 3p^2 \)
- **Phosphorus (P)**: Atomic number 15
- Electronic configuration: \( 1s^2 2s^2 2p^6 3s^2 3p^3 \)
- **Sulfur (S)**: Atomic number 16
- Electronic configuration: \( 1s^2 2s^2 2p^6 3s^2 3p^4 \)

3. **Apply the Octet Rule**:
- The octet rule states that atoms tend to bond in such a way that they have eight electrons in their valence shell, achieving a stable noble gas configuration.

4. **Analyze Each Element**:
- **Carbon (C)**:
- Valence electrons: 4 (2 from \( 2s \) and 2 from \( 2p \))
- When forming \( CH_3 \), it has 7 electrons (4 from carbon + 3 from hydrogen), leaving it with one unpaired electron (free radical), making it unstable.

- **Silicon (Si)**:
- Valence electrons: 4 (2 from \( 3s \) and 2 from \( 3p \))
- When forming \( SiH_3 \), it also has 7 electrons, leading to a free radical, hence unstable.

- **Phosphorus (P)**:
- Valence electrons: 5 (2 from \( 3s \) and 3 from \( 3p \))
- When forming \( PH_3 \), it has 8 electrons (5 from phosphorus + 3 from hydrogen), achieving a stable octet configuration.

- **Sulfur (S)**:
- Valence electrons: 6 (2 from \( 3s \) and 4 from \( 3p \))
- When forming \( SH_3 \), it has 9 electrons (6 from sulfur + 3 from hydrogen), which exceeds the octet and introduces instability due to the presence of unpaired electrons.

5. **Conclusion**:
- The only element that forms a stable \( XH_3 \) species without any free radicals is **Phosphorus (P)**, resulting in \( PH_3 \).

### Final Answer:
The element for which \( XH_3 \) is a stable species is **Phosphorus (P)**.