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 need to analyze each compound and identify the nature of the bonds present. A coordinate bond (or dative bond) is formed when both electrons in the bond come from the same atom. Let's evaluate each option step by step.

### Step 1: Analyze H3O+
- **Structure**: H3O+ (Hydronium ion) consists of one oxygen atom bonded to three hydrogen atoms.
- **Valency**: Oxygen has a valency of 2, and hydrogen has a valency of 1.
- **Bonding**: In H3O+, one of the hydrogen atoms forms a coordinate bond with the lone pair of electrons on the oxygen atom.
- **Conclusion**: H3O+ contains a coordinate bond.

### Step 2: Analyze BF4-
- **Structure**: BF4- (Tetrafluoroborate ion) consists of one boron atom bonded to four fluorine atoms.
- **Valency**: Boron has a valency of 3, and fluorine has a valency of 1.
- **Bonding**: In BF4-, one of the fluorine atoms donates a pair of electrons to boron, forming a coordinate bond.
- **Conclusion**: BF4- contains a coordinate bond.

### Step 3: Analyze HF2-
- **Structure**: HF2- (Dihydrogen fluoride ion) consists of one fluorine atom bonded to two hydrogen atoms.
- **Valency**: Hydrogen has a valency of 1, and fluorine has a valency of 1.
- **Bonding**: The bonding in HF2- is primarily due to hydrogen bonding rather than coordinate bonding. The two hydrogen atoms are bonded to fluorine through regular covalent bonds.
- **Conclusion**: HF2- does not contain a coordinate bond.

### Step 4: Analyze NH4+
- **Structure**: NH4+ (Ammonium ion) consists of one nitrogen atom bonded to four hydrogen atoms.
- **Valency**: Nitrogen has a valency of 3, and hydrogen has a valency of 1.
- **Bonding**: In NH4+, one of the hydrogen atoms forms a coordinate bond with the lone pair of electrons on the nitrogen atom.
- **Conclusion**: NH4+ contains a coordinate bond.

### Final Conclusion:
Among the options analyzed, **HF2-** is the only compound that does not contain a coordinate bond.

### Answer:
The compound that does not contain a coordinate bond is **HF2-** (Option C).

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