Which of the following does not contain a coordinate bond?

Options

A. `H_(3)O^(+)`
B. `BF_(4)^(-)`
C. `HF_(2)^(-)`
D. `NH_(4)^(+)`

Answer

To determine which of the given options does not contain a coordinate bond, we will analyze each option step by step.

### Step 1: Understand Coordinate Bonds
A coordinate bond (or dative bond) is formed when one atom donates a pair of electrons to another atom that has an empty orbital. This typically occurs between a Lewis base (which has a lone pair of electrons) and a Lewis acid (which has an empty orbital).

### Step 2: Analyze Each Option

**Option 1: H3O⁺ (Hydronium Ion)**
- **Structure**: The water molecule (H2O) has two lone pairs on the oxygen atom. When one of these lone pairs is donated to a hydrogen ion (H⁺), a coordinate bond is formed.
- **Conclusion**: H3O⁺ contains a coordinate bond.

**Option 2: BF4⁻ (Tetrafluoroborate Ion)**
- **Structure**: BF3 has an empty p-orbital on boron. When a fluoride ion (F⁻) donates a lone pair to boron, a coordinate bond is formed.
- **Conclusion**: BF4⁻ contains a coordinate bond.

**Option 3: HF2⁻ (Dihydrogen Fluoride Ion)**
- **Structure**: HF2⁻ can be represented as having strong hydrogen bonding between the hydrogen and fluorine atoms. The bond between H and F does not involve a lone pair donation from one atom to another, but rather involves hydrogen bonding.
- **Conclusion**: HF2⁻ does not contain a coordinate bond due to the presence of strong hydrogen bonding.

**Option 4: NH4⁺ (Ammonium Ion)**
- **Structure**: Ammonia (NH3) has a lone pair on the nitrogen atom. When it donates this lone pair to a hydrogen ion (H⁺), a coordinate bond is formed.
- **Conclusion**: NH4⁺ contains a coordinate bond.

### Final Answer
Based on the analysis, the option that does not contain a coordinate bond is **HF2⁻**.

### Summary of Steps:
1. Understand what a coordinate bond is.
2. Analyze each option for the presence of coordinate bonds.
3. Conclude that HF2⁻ does not contain a coordinate bond due to strong hydrogen bonding.