Which of the following is a Lewis base?

Options

A. `H_(2)O`
B. `CI^(Theta)`
C. `BF_(3)`
D. `NH_(3)`

Explanation

To determine which of the given options is a Lewis base, we need to understand the definition of a Lewis base. A Lewis base is defined as a substance that can donate an electron pair to form a covalent bond.

Let's analyze the options one by one:

1. **H₂O (Water)**:
- Water has two lone pairs of electrons on the oxygen atom.
- It can donate one of these lone pairs to a Lewis acid, thus acting as a Lewis base.
- **Conclusion**: H₂O is a Lewis base.

2. **Cl⁻ (Chloride Ion)**:
- The chloride ion has three lone pairs of electrons.
- It can donate one of these lone pairs to a Lewis acid, therefore it also acts as a Lewis base.
- **Conclusion**: Cl⁻ is a Lewis base.

3. **BF₃ (Boron Trifluoride)**:
- Boron trifluoride has an incomplete octet and can accept an electron pair.
- It does not donate an electron pair; instead, it acts as a Lewis acid.
- **Conclusion**: BF₃ is not a Lewis base.

4. **NH₃ (Ammonia)**:
- Ammonia has one lone pair of electrons on the nitrogen atom.
- It can donate this lone pair to a Lewis acid, thus acting as a Lewis base.
- **Conclusion**: NH₃ is a Lewis base.

**Final Answer**: The Lewis bases among the options are H₂O, Cl⁻, and NH₃.