The smallest size cation and anion that can exist are respectively 

Options

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

Answer

To determine the smallest size cation and anion that can exist, we can follow these steps:

### Step 1: Understand the Definitions
- **Cation**: A positively charged ion formed when an atom loses one or more electrons.
- **Anion**: A negatively charged ion formed when an atom gains one or more electrons.

### Step 2: Identify the Smallest Cation
- Among the cations, we can compare **H⁺ (hydrogen ion)** and **Li⁺ (lithium ion)**.
- Both hydrogen and lithium are in the same group (Group 1) of the periodic table.
- As we move down a group, the size of the atoms increases due to the addition of electron shells.
- Therefore, **H⁺** is smaller than **Li⁺** because H has fewer electron shells.

### Step 3: Identify the Smallest Anion
- For anions, we can compare **F⁻ (fluoride ion)** and **H⁻ (hydride ion)**.
- The size of anions is influenced by the electron-to-proton ratio.
- For **H⁻**, the ratio is 2 electrons to 1 proton (2:1), while for **F⁻**, the ratio is 10 electrons to 9 protons (10:9).
- A higher electron-to-proton ratio typically leads to a larger size. Therefore, since H⁻ has a lower ratio than F⁻, **H⁻** is smaller than **F⁻**.

### Step 4: Conclusion
- The smallest cation is **H⁺**.
- The smallest anion is **H⁻**.

### Final Answer
The smallest size cation and anion that can exist are respectively **H⁺** and **H⁻**.

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