The following species cannot exist in an aqueous solution?

Options

A. `NH_(4)^(+)`
B. `NH_(3)^(-)`
C. `NH_(3)`
D. `NH_(2)^(-)`

Answer

To determine which species cannot exist in an aqueous solution, we will analyze each of the given species: NH4⁺, NH3⁻, NH3, and NH2⁻.

### Step-by-Step Solution:

1. **Identify the Species**: We have four species to consider: NH4⁺ (ammonium ion), NH3⁻ (amide ion), NH3 (ammonia), and NH2⁻ (amide ion).

2. **Analyze NH4⁺**:
- NH4⁺ is the ammonium ion. In an aqueous solution, it can exist because it is a stable ion formed from the protonation of ammonia (NH3).
- **Conclusion**: NH4⁺ can exist in aqueous solution.

3. **Analyze NH3**:
- NH3 is ammonia. When dissolved in water, it can act as a weak base and partially dissociate to form NH4⁺ and OH⁻.
- **Conclusion**: NH3 can exist in aqueous solution.

4. **Analyze NH2⁻**:
- NH2⁻ is the amide ion. It is a strong base and can react with water to produce NH3 and OH⁻.
- **Conclusion**: NH2⁻ can exist in aqueous solution.

5. **Analyze NH3⁻**:
- NH3⁻ is the amide ion, which is a very strong base and is not stable in aqueous solution. It would react with water very vigorously and is not commonly found in this state.
- **Conclusion**: NH3⁻ cannot exist in aqueous solution.

### Final Answer:
The species that cannot exist in an aqueous solution is **NH3⁻**.

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