Which of the following is electron precise hydride ?

Options

A. `BH_(3)`
B. `CH_(4)`
C. `H_(2)O`
D. HF

Answer

To determine which of the following is an electron-precise hydride, we need to analyze the options based on the group of elements they belong to and their electron configurations.

### Step-by-Step Solution:

1. **Understand Electron Precise Hydrides**:
- Electron-precise hydrides are formed by elements that have a complete octet, meaning they have the exact number of electrons needed to form stable covalent bonds. Typically, these are formed by elements from Group 14.

2. **Analyze the Options**:
- **Option 1: BCl3 (Boron Trichloride)**:
- Boron belongs to Group 13.
- Boron typically forms electron-deficient hydrides because it does not have a complete octet (it has 6 electrons in its valence shell).
- **Conclusion**: BCl3 is an electron-deficient hydride.

- **Option 2: CH4 (Methane)**:
- Carbon belongs to Group 14.
- Carbon forms four bonds in CH4, which allows it to have a complete octet (8 electrons).
- **Conclusion**: CH4 is an electron-precise hydride.

- **Option 3: H2O (Water)**:
- Oxygen belongs to Group 16.
- In H2O, oxygen has 8 electrons (6 from itself and 2 from the two hydrogen atoms), which means it has more than the required number of electrons for a stable structure.
- **Conclusion**: H2O is an electron-rich hydride.

- **Option 4: HF (Hydrogen Fluoride)**:
- Fluorine belongs to Group 17.
- In HF, fluorine has 8 electrons (7 from itself and 1 from hydrogen), which is also more than the required number for a stable structure.
- **Conclusion**: HF is an electron-rich hydride.

3. **Final Conclusion**:
- Based on the analysis, the only electron-precise hydride among the options is **CH4** (Option 2).

### Answer:
**The electron-precise hydride is CH4.**