Which one of the following alkali metals gives hydrated salts ?

Options

A. LI
B. Na
C. K
D. Cs

Explanation

To determine which alkali metal gives hydrated salts, we can follow these steps:

### Step 1: Understand Hydration
Hydration refers to the process where water molecules surround and interact with ions. For a metal ion to form hydrated salts, it must be able to attract and hold onto water molecules.

**Hint:** Hydration is influenced by the ability of the metal ion to attract water molecules.

### Step 2: Consider Charge Density
Charge density is defined as the charge of an ion divided by its volume. It is an important factor in determining how well an ion can attract water molecules.

**Hint:** Smaller ions with higher charge density will generally attract water molecules more effectively.

### Step 3: Compare Sizes of Alkali Metal Ions
Among the alkali metals listed (Lithium, Sodium, Potassium, and Cesium), we need to compare their ionic sizes. Lithium ion (Li⁺) is the smallest, while Cesium ion (Cs⁺) is the largest.

**Hint:** Remember that as the size of the ion increases, the charge density decreases.

### Step 4: Analyze Charge Densities
- **Lithium (Li⁺)**: Smallest size, highest charge density.
- **Sodium (Na⁺)**: Larger than Li⁺, lower charge density than Li⁺.
- **Potassium (K⁺)**: Larger than Na⁺, even lower charge density.
- **Cesium (Cs⁺)**: Largest size, lowest charge density.

**Hint:** The smaller the ion, the greater the charge density and the better it can hydrate.

### Step 5: Conclusion
Since lithium ion (Li⁺) has the highest charge density among the alkali metals listed, it is the most capable of hydrating and thus forms hydrated salts.

**Final Answer:** **Lithium (Li)** is the alkali metal that gives hydrated salts.