Which of the following metals can easily be cut with a knife?

Options

A. Magnesium
B. Barium
C. Aluminium
D. Sodium

Answer

To determine which of the given metals can be easily cut with a knife, we need to analyze the properties of each metal listed in the options: magnesium, barium, aluminium, and sodium.

### Step-by-Step Solution:

1. **Identify the Metals and Their Groups**:
- Magnesium (Mg) is in Group 2 (alkaline earth metals).
- Barium (Ba) is also in Group 2 (alkaline earth metals).
- Aluminium (Al) is in Group 13 (p-block element).
- Sodium (Na) is in Group 1 (alkali metals).

2. **Understand the Properties of the Metals**:
- Softness is a key property that allows a metal to be cut easily with a knife. Generally, alkali metals (Group 1) are known for their softness.
- Group 2 metals (like magnesium and barium) are harder compared to alkali metals.
- Aluminium, while it can be worked with, is not as soft as alkali metals.

3. **Identify the Soft Metals**:
- The alkali metals (Group 1) are known to be soft and can be easily cut with a knife. This includes lithium, sodium, potassium, rubidium, cesium, and francium.

4. **Evaluate the Options**:
- **Magnesium**: Hard, not easily cut.
- **Barium**: Hard, not easily cut.
- **Aluminium**: Moderately hard, not easily cut.
- **Sodium**: Soft, can be easily cut with a knife.

5. **Conclusion**:
- Among the given options, sodium is the only metal that can be easily cut with a knife.

### Final Answer:
The metal that can easily be cut with a knife is **sodium**.