Number of electron deficient molecules among the following
`PH_(3),B_(2)H_(6) ,C Cl_(4),NH_(3),LiH and BCl_(3) `is

Options

A. 0
B. 1
C. 2
D. 3

Explanation

To determine the number of electron deficient molecules among the given options: `PH3, B2H6, CCl4, NH3, LiH, and BCl3`, we will analyze each molecule based on the concept of electron deficiency.

### Step-by-Step Solution:

1. **Understanding Electron Deficiency**:
- Electron deficient molecules are those that have fewer than 8 electrons in their valence shell, which makes them capable of accepting electrons (Lewis acids).

2. **Analyzing Each Compound**:
- **PH3 (Phosphine)**:
- Phosphorus has 5 valence electrons, and in PH3, it shares 3 electrons with hydrogen, making a total of 8 electrons.
- **Conclusion**: Not electron deficient.

- **B2H6 (Diborane)**:
- Each boron atom has 3 valence electrons. In B2H6, the boron atoms are bonded to hydrogen and share electrons in a way that leaves boron with only 6 electrons in total.
- **Conclusion**: Electron deficient.

- **CCl4 (Carbon Tetrachloride)**:
- Carbon has 4 valence electrons and forms 4 bonds with chlorine atoms, achieving a total of 8 electrons in its valence shell.
- **Conclusion**: Not electron deficient.

- **NH3 (Ammonia)**:
- Nitrogen has 5 valence electrons and shares 3 with hydrogen, resulting in a total of 8 electrons.
- **Conclusion**: Not electron deficient.

- **LiH (Lithium Hydride)**:
- Lithium has 1 valence electron and shares it with hydrogen, resulting in only 2 electrons around lithium.
- **Conclusion**: Electron deficient.

- **BCl3 (Boron Trichloride)**:
- Boron has 3 valence electrons and forms 3 bonds with chlorine atoms, resulting in only 6 electrons around boron.
- **Conclusion**: Electron deficient.

3. **Counting the Electron Deficient Molecules**:
- From the analysis, the electron deficient molecules are:
- B2H6
- LiH
- BCl3
- Total: 3 electron deficient molecules.

### Final Answer:
The number of electron deficient molecules among the given options is **3**.

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