The alkali metals have low melting point. Which of the following alkali metal is expected to melt if the room temperature rises to `30^(@)C` ?

Options

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

Explanation

To determine which alkali metal is expected to melt if the room temperature rises to 30°C, we need to consider the melting points of the alkali metals. Here’s a step-by-step solution:

### Step 1: Identify the Alkali Metals
The alkali metals include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

### Step 2: Know the Melting Points
We need to know the melting points of these alkali metals:
- Lithium (Li): ~180.5°C
- Sodium (Na): ~97.8°C
- Potassium (K): ~63.5°C
- Rubidium (Rb): ~39.3°C
- Cesium (Cs): ~28.5°C
- Francium (Fr): ~27°C (not commonly encountered due to its radioactivity)

### Step 3: Compare Melting Points with Room Temperature
Room temperature is considered to be around 30°C. We need to find which alkali metal has a melting point close to or below this temperature:
- Cesium (Cs) has a melting point of approximately 28.5°C, which is below 30°C.
- Rubidium (Rb) has a melting point of approximately 39.3°C, which is above 30°C.
- All other alkali metals have melting points significantly higher than 30°C.

### Step 4: Conclusion
Since cesium has a melting point of approximately 28.5°C, it is the only alkali metal that is expected to melt when the room temperature rises to 30°C.

### Final Answer
The alkali metal that is expected to melt if the room temperature rises to 30°C is **Cesium (Cs)**.

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