The correct order of decreasing radius of aquated `Na^(+), K^(+) " and " Li^(+)` is:

Options

A. `Na^(+) (aq) gt K^(+)(aq) gt Li^(+)(aq)`
B. `K^(+)(aq) gt Na^(+)(aq) gt Li^(+)(aq)`
C. `Li^(+)(aq) gt Na^(+)(aq) gt K^(+) (aq)`
D. `K^(+) (aq) gt Li^(+)(aq) gt Na^(+) (aq)`

Explanation

To determine the correct order of decreasing radius of aquated \( \text{Na}^+, \text{K}^+, \) and \( \text{Li}^+ \), we need to analyze the hydrated radii of these ions.

### Step-by-Step Solution:

1. **Understanding the Concept of Hydrated Radius**:
- The hydrated radius refers to the effective radius of an ion when it is surrounded by water molecules in an aqueous solution. This is influenced by the size of the ion and its charge.

2. **Identify the Size of the Ions**:
- The ions in question are \( \text{Li}^+, \text{Na}^+, \) and \( \text{K}^+ \).
- Among these, \( \text{Li}^+ \) is the smallest ion, followed by \( \text{Na}^+ \), and then \( \text{K}^+ \) which is the largest.

3. **Relate Ion Size to Hydration**:
- The smaller the ion, the greater the extent of hydration. This is because smaller ions can attract more water molecules due to their higher charge density.
- Conversely, larger ions like \( \text{K}^+ \) will have fewer water molecules surrounding them because their larger size means they exert a weaker attraction on water molecules.

4. **Determine the Order of Hydrated Radii**:
- Since \( \text{Li}^+ \) is the smallest, it will have the largest hydrated radius, followed by \( \text{Na}^+ \), and then \( \text{K}^+ \) which will have the smallest hydrated radius.
- Therefore, the order of decreasing hydrated radius is:
\[ \text{Li}^+ > \text{Na}^+ > \text{K}^+ \]

5. **Conclusion**:
- The correct order of decreasing radius of aquated \( \text{Na}^+, \text{K}^+, \) and \( \text{Li}^+ \) is:
\[ \text{Li}^+ > \text{Na}^+ > \text{K}^+ \]

### Final Answer:
The correct order of decreasing radius of aquated \( \text{Na}^+, \text{K}^+, \) and \( \text{Li}^+ \) is:
\[ \text{Li}^+ > \text{Na}^+ > \text{K}^+ \]