Which of the following hydrides is electron-precise hydride ?

Options

A. `B_(2)H_(6)`
B. `NH_(3)`
C. `H_(2)O`
D. `CH_(4)`

Explanation

To determine which of the following hydrides is an electron-precise hydride, we first need to understand what an electron-precise hydride is. Electron-precise hydrides are those that have an exact number of electrons in their outer shell to form normal covalent bonds.

Let's analyze the given hydrides one by one:

1. **B2H6 (Diborane)**:
- Structure: B2H6 consists of two boron atoms and six hydrogen atoms. Each boron atom forms four bonds with hydrogen atoms.
- Electron Count: Boron typically has three valence electrons, and in B2H6, the boron atoms are electron-deficient as they do not have a complete octet. Therefore, B2H6 is an electron-deficient hydride.

2. **NH3 (Ammonia)**:
- Structure: NH3 consists of one nitrogen atom and three hydrogen atoms. The nitrogen atom has one lone pair.
- Electron Count: Nitrogen has five valence electrons, and in NH3, it shares three electrons with hydrogen and has one lone pair. This means NH3 has an excess of electrons, making it an electron-rich hydride.

3. **H2 (Dihydrogen)**:
- Structure: H2 consists of two hydrogen atoms.
- Electron Count: Each hydrogen atom has one electron, and when they bond, they share their electrons to form a single covalent bond. H2 does not have any excess or deficiency of electrons, but it is not typically classified as an electron-precise hydride.

4. **CH4 (Methane)**:
- Structure: CH4 consists of one carbon atom and four hydrogen atoms. The carbon atom forms four covalent bonds with the hydrogen atoms.
- Electron Count: Carbon has four valence electrons and shares them with four hydrogen atoms, achieving a complete octet. Thus, CH4 has no excess or deficiency of electrons, making it an electron-precise hydride.

Based on the analysis, the hydride that is classified as an electron-precise hydride is **CH4 (Methane)**.

### Summary:
- **B2H6**: Electron-deficient hydride
- **NH3**: Electron-rich hydride
- **H2**: Not classified as electron-precise
- **CH4**: Electron-precise hydride (Correct answer)

### Final Answer:
**CH4 (Methane)** is the electron-precise hydride.