The alkali metals are characterised by which of the following properties ?

Options

A. High boiling point
B. High density
C. High negative standards electrode potential
D. Large atomic size

Answer

To answer the question regarding the properties characterizing alkali metals, we can analyze each option provided.

### Step-by-Step Solution:

1. **Understanding Alkali Metals**: Alkali metals are located in Group 1 of the periodic table and include elements like lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). They are known for their unique properties due to their single valence electron.

2. **Evaluating the Options**:
- **Option A: High Boiling Point**: Alkali metals do not have high boiling points. In fact, they have relatively low boiling and melting points compared to other metals. This is due to the weak metallic bonding resulting from having only one unpaired electron.
- **Option B: High Density**: Alkali metals generally have low densities. As we move down the group, the density may increase slightly, but they remain less dense than many other metals.
- **Option C: High Negative Electrode Potential**: This is correct. Alkali metals have a high negative electrode potential, indicating that they are easily oxidized (they lose electrons readily) and act as good reducing agents.
- **Option D: Large Atomic Size**: This is also correct. Alkali metals have the largest atomic sizes in their respective periods due to their single valence electron and the resulting shielding effect.

3. **Conclusion**: The properties that characterize alkali metals are:
- Large atomic size (correct)
- High negative electrode potential (correct)

### Final Answer:
The alkali metals are characterized by:
- Large atomic size
- High negative electrode potential