The elements of group II are known as alkaline earth metals. The electronic configuration of these elements is `ns^(2)` and oxidation state is `+2`. They have higher ionization energy than alkali metals in their respective period due to their small size and completely filled s-orbital. These elements give characteristic colour to bunsen flame. magnesium is used in the preparation of Grignard agent (RMgX) which is used in organic chemistry for preparation of sevaral organic compounds like alcohols. acids, hydrocarbons.
Q. The correct order of 1st ionization energy is

Options

A. `Na lt Mg lt Al`
B. `Na lt Al lt Mg`
C. `Al lt Mg lt Na`
D. `Ag lt Na lt Mg`

Answer

To determine the correct order of first ionization energy among sodium (Na), magnesium (Mg), and aluminum (Al), we need to analyze the factors that influence ionization energy.

### Step-by-Step Solution:

1. **Understanding Ionization Energy**:
- Ionization energy is the energy required to remove one electron from the outermost shell of an atom. Higher ionization energy means it is more difficult to remove an electron.

2. **Position in the Periodic Table**:
- Sodium (Na) is an alkali metal in Group 1, while magnesium (Mg) and aluminum (Al) are in Group 2 and Group 13, respectively, in the same period (Period 3).

3. **Trends in Ionization Energy**:
- Ionization energy generally increases across a period from left to right due to increasing nuclear charge (more protons in the nucleus) which holds the electrons more tightly.
- Conversely, ionization energy decreases down a group due to increased atomic size and shielding effect.

4. **Comparing Sodium, Magnesium, and Aluminum**:
- Sodium has the lowest ionization energy among the three because it has a single electron in its outermost shell (3s¹) which is easier to remove.
- Magnesium has a higher ionization energy than sodium because it has a completely filled s-orbital (3s²), making it more stable and harder to remove an electron.
- Aluminum has a higher ionization energy than sodium but lower than magnesium. This is because aluminum has a partially filled p-orbital (3s² 3p¹), and removing an electron from a p-orbital requires less energy compared to removing from a filled s-orbital.

5. **Conclusion**:
- Therefore, the correct order of first ionization energy is:
- **Mg > Al > Na**

### Final Answer:
The correct order of first ionization energy is: **Magnesium (Mg) > Aluminum (Al) > Sodium (Na)**.