Moleular hydrides are classified as electron deficient, electron precise and electron rich compounds. Explain each type with two examples.

Explanation

To classify molecular hydrides into three categories—electron deficient, electron precise, and electron rich—let's explore each type in detail along with two examples for each.

### Step 1: Electron Deficient Hydrides
- **Definition**: Electron deficient hydrides are those in which the central atom has an incomplete octet. This means that the central atom does not have enough electrons to complete its octet, making it electron deficient.
- **Formation**: These hydrides are typically formed by elements from Group 13 of the periodic table.
- **Examples**:
1. **Boron Hydride (BH3)**: Boron has three valence electrons and forms three bonds with hydrogen atoms, resulting in only six electrons around it. Thus, it has an incomplete octet.
2. **Aluminum Hydride (AlH3)**: Similar to boron, aluminum has three valence electrons and forms three bonds with hydrogen, also resulting in an incomplete octet with only six electrons.

### Step 2: Electron Precise Hydrides
- **Definition**: Electron precise hydrides have the exact number of electrons required to form normal covalent bonds, meaning they have a complete octet.
- **Formation**: These hydrides are typically formed by elements from Group 14 of the periodic table.
- **Examples**:
1. **Methane (CH4)**: Carbon has four valence electrons and forms four bonds with hydrogen, resulting in a complete octet with eight electrons around it.
2. **Silane (SiH4)**: Silicon, like carbon, has four valence electrons and forms four bonds with hydrogen, achieving a complete octet.

### Step 3: Electron Rich Hydrides
- **Definition**: Electron rich hydrides contain excess electrons, which are often present as lone pairs on the central atom. These hydrides can donate these lone pairs, making them act as Lewis bases.
- **Formation**: These hydrides are typically formed by elements from Groups 15, 16, and 17 of the periodic table.
- **Examples**:
1. **Ammonia (NH3)**: Nitrogen has five valence electrons and forms three bonds with hydrogen, leaving one lone pair of electrons, making it electron rich.
2. **Water (H2O)**: Oxygen has six valence electrons and forms two bonds with hydrogen, leaving two lone pairs of electrons, making it electron rich.

### Summary
- **Electron Deficient Hydrides**: BH3, AlH3 (incomplete octet)
- **Electron Precise Hydrides**: CH4, SiH4 (complete octet)
- **Electron Rich Hydrides**: NH3, H2O (excess electrons as lone pairs)