The ionisation energy of potassium is lower than that of sodium. Give reason.

Explanation

**Step-by-Step Solution:**

1. **Understanding Ionization Energy**:
- Ionization energy is defined as the minimum amount of energy required to remove an electron from the outermost shell of an isolated atom.

2. **Electronic Configuration of Sodium**:
- Sodium (Na) has an atomic number of 11, which means it has 11 electrons.
- The electronic configuration of sodium is:
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