Name the classes of hydrides to which `H_(2)O, B_(2)H_(6)` and NaH belong.

Explanation

To classify the hydrides \( H_2O \), \( B_2H_6 \), and \( NaH \), we can follow these steps:

### Step 1: Classify \( H_2O \) (Water)
- **Identify the central atom**: In water, the central atom is oxygen.
- **Determine the bonding type**: Oxygen is a non-metal and forms covalent bonds with hydrogen by sharing electrons.
- **Structure of \( H_2O \)**: The structure consists of two hydrogen atoms covalently bonded to one oxygen atom, with two lone pairs of electrons on the oxygen.
- **Classify the hydride**: Since it involves covalent bonding and has lone pairs of electrons, \( H_2O \) is classified as a **covalent hydride** and specifically as an **electron-rich hydride** due to the presence of lone pairs.

### Step 2: Classify \( B_2H_6 \) (Diborane)
- **Identify the central atoms**: The central atoms are boron.
- **Determine the bonding type**: Boron also forms covalent bonds. In \( B_2H_6 \), there are two terminal hydrogen atoms and two bridging hydrogen atoms.
- **Structure of \( B_2H_6 \)**: The structure includes three-center two-electron bonds (banana bonds) between boron and hydrogen.
- **Count the valence electrons**: Boron has 3 valence electrons, and with 2 boron atoms and 6 hydrogen atoms, we have a total of 12 electrons available. However, to form the required bonds, we need 16 electrons, indicating that \( B_2H_6 \) is **electron-deficient**.
- **Classify the hydride**: Therefore, \( B_2H_6 \) is classified as a **covalent hydride** and specifically as an **electron-deficient hydride**.

### Step 3: Classify \( NaH \) (Sodium Hydride)
- **Identify the nature of sodium**: Sodium is a metal and tends to lose electrons.
- **Determine the bonding type**: Sodium forms ionic bonds with hydrogen.
- **Structure of \( NaH \)**: Sodium donates an electron to hydrogen, resulting in the formation of \( Na^+ \) and \( H^- \).
- **Classify the hydride**: Thus, \( NaH \) is classified as an **ionic or saline hydride**.

### Final Classification
- \( H_2O \) is a **covalent hydride** and **electron-rich hydride**.
- \( B_2H_6 \) is a **covalent hydride** and **electron-deficient hydride**.
- \( NaH \) is an **ionic or saline hydride**.

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