The first ionisation potential of `Na,Mg,Al` and `Si` are in the order

Options

A. `NaltAlltMgltSi`
B. `NagtMggtAlgtSi`
C. `NaltMgltAlltSi`
D. `NagtMggtAlltSi`

Explanation

To determine the order of first ionization potential for the elements Sodium (Na), Magnesium (Mg), Aluminum (Al), and Silicon (Si), we need to consider several factors that influence ionization energy.

### Step-by-Step Solution:

1. **Understanding Ionization Potential**:
- Ionization potential (or ionization energy) is defined as the energy required to remove an electron from an isolated gaseous atom.
- It is generally expressed in electron volts (eV) or kilojoules per mole (kJ/mol).

2. **Trends in the Periodic Table**:
- Ionization potential tends to increase across a period from left to right due to increasing nuclear charge, which attracts the electrons more strongly.
- Conversely, ionization potential decreases down a group as the atomic size increases, leading to a weaker attraction between the nucleus and the outermost electrons.

3. **Analyzing the Elements**:
- Sodium (Na) has the electron configuration of [Ne] 3s¹. It has one electron in its outermost shell, making it easier to remove.
- Magnesium (Mg) has the electron configuration of [Ne] 3s². It has two electrons in its outer shell, requiring more energy to remove one compared to Na.
- Aluminum (Al) has the electron configuration of [Ne] 3s² 3p¹. It has three outer electrons, and while it is easier to remove one of the p electrons, it is still more than Mg.
- Silicon (Si) has the electron configuration of [Ne] 3s² 3p². It has four outer electrons, and due to its higher nuclear charge and smaller size compared to the others, it has the highest ionization potential.

4. **Order of Ionization Potential**:
- Based on the above analysis, the order of first ionization potential from lowest to highest is:
- Sodium (Na) < Aluminum (Al) < Magnesium (Mg) < Silicon (Si).

### Final Order:
- **Sodium (Na) < Aluminum (Al) < Magnesium (Mg) < Silicon (Si)**