Which of the following is not the characteristics of alkali metals?

Options

A. Low melting point
B. Low electronegativity
C. High ionisation energies
D. Highest reducing power in its period

Explanation

To determine which of the following is not a characteristic of alkali metals, we need to analyze each option provided:

1. **Option A: Low melting point**
Alkali metals are known to have low melting points compared to other metals. As we move down the group in the periodic table, the melting points of alkali metals decrease due to the weakening of metallic bonds. Thus, this statement is true for alkali metals.

2. **Option B: Low electronegativity**
Alkali metals have low electronegativity values. This is because they have larger atomic sizes, which results in a weaker attraction between the nucleus and the valence electrons. Hence, this statement is also true for alkali metals.

3. **Option C: High ionization energy**
Alkali metals actually have low ionization energies. The larger atomic size means that the outermost electron is further from the nucleus and experiences less attraction, making it easier to remove. Therefore, this statement is false for alkali metals.

4. **Option D: High reducing power**
Alkali metals are known for their high reducing power due to their low ionization energy. They can easily lose their outermost electron, which allows them to act as effective reducing agents. Thus, this statement is true for alkali metals.

Based on this analysis, the option that is not a characteristic of alkali metals is **Option C: High ionization energy**.

### Summary of the Solution:
- **Correct Answer:** Option C: High ionization energy