Arrange the following in increasing order :
First ionisation enthalpy : `Mg , Al, Si, Na`

Explanation

To arrange the elements Mg (Magnesium), Al (Aluminum), Si (Silicon), and Na (Sodium) in increasing order of their first ionization enthalpy, we need to consider their positions in the periodic table and the general trends of ionization energy.

### Step-by-Step Solution:

1. **Understanding Ionization Energy**:
- Ionization energy is the energy required to remove the outermost electron from an atom. It generally increases across a period (from left to right) and decreases down a group (from top to bottom) in the periodic table.

2. **Identify the Elements and Their Positions**:
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