The smallest cation and the smallest anion are respectively

Options

A. `H^(+)` and `H^(-)`
B. `H^(+)` and `F^(-)`
C. `Li^(+)` and `H^(-)`
D. `Li^(+)` and `F^(-)`

Answer

To determine the smallest cation and the smallest anion, we need to analyze the properties of cations and anions based on their size and charge.

### Step-by-Step Solution:

1. **Understanding Cations and Anions**:
- Cations are positively charged ions formed when an atom loses one or more electrons.
- Anions are negatively charged ions formed when an atom gains one or more electrons.

2. **Identifying the Smallest Cation**:
- The smallest cation is typically the one with the least number of electrons and a positive charge.
- Among the common cations, hydrogen (H⁺) and lithium (Li⁺) are considered.
- Hydrogen has only one proton and one electron, while lithium has three protons and three electrons.
- Therefore, H⁺, which has no electrons, is smaller than Li⁺.

3. **Identifying the Smallest Anion**:
- The smallest anion is the one with the least number of electrons and a negative charge.
- Common anions include fluoride (F⁻) and hydride (H⁻).
- Fluoride has nine protons and ten electrons, while hydride has one proton and two electrons.
- The electron-to-proton ratio is crucial here. For H⁻, the ratio is 2:1, and for F⁻, it is 10:9.
- A higher electron-to-proton ratio indicates a larger size. Thus, H⁻ is smaller than F⁻.

4. **Conclusion**:
- The smallest cation is H⁺ (hydrogen ion).
- The smallest anion is H⁻ (hydride ion).

### Final Answer:
- The smallest cation is H⁺ (hydrogen ion).
- The smallest anion is H⁻ (hydride ion).