Atoms of metals have only a few electrons in their valence shells while atoms of non-metals generally have more electrons in their valence shells. Metallic character is closely related to atomic radius and ionisation enthalpy. Metallic character increases from top to bottom in a group and decreases from left to right in a period. Metallic character is inversely related to electronegativity.
Considering the elements B, Al, Mg and K, the correct order of their ionisation potential is

Options

A. `B gt Al gt Mg gt K`
B. `Al gt K gt B gt Mg`
C. `Mg gt Al gt K gt B`
D. `K gt Mg gt Al gt B`

Answer

To determine the correct order of ionization potential for the elements B (Boron), Al (Aluminum), Mg (Magnesium), and K (Potassium), we need to consider the following steps:

### Step 1: Understand Ionization Potential
Ionization potential (or ionization energy) is the minimum amount of energy required to remove an electron from an isolated gaseous atom.

**Hint:** Remember that ionization energy is influenced by the atomic size and the number of electrons in the outer shell.

### Step 2: Identify the Periods and Groups
- Boron (B) is in Period 2, Group 13.
- Aluminum (Al) is in Period 3, Group 13.
- Magnesium (Mg) is in Period 3, Group 2.
- Potassium (K) is in Period 4, Group 1.

**Hint:** Knowing the position of each element in the periodic table helps predict trends in ionization energy.

### Step 3: Analyze Atomic Size Trends
- Atomic size decreases across a period (left to right) due to increasing nuclear charge.
- Atomic size increases down a group (top to bottom) due to the addition of electron shells.

**Hint:** Larger atoms have lower ionization energy because the outer electrons are further from the nucleus and are held less tightly.

### Step 4: Compare Atomic Sizes
- Boron (B) has the smallest atomic size (2nd period).
- Magnesium (Mg) and Aluminum (Al) are in the 3rd period, but Mg is smaller than Al because Mg is in Group 2 and Al is in Group 13.
- Potassium (K) is in the 4th period and has the largest atomic size among the four.

**Hint:** Remember that the larger the atomic size, the lower the ionization potential.

### Step 5: Determine Ionization Potential Order
Based on the atomic sizes:
- Potassium (K) has the largest size, hence the lowest ionization potential.
- Magnesium (Mg) is smaller than Aluminum (Al), so it has a higher ionization potential than Al.
- Boron (B) has the smallest size, thus the highest ionization potential.

**Final Order of Ionization Potential:**
1. K (Potassium) - Lowest Ionization Potential
2. Al (Aluminum)
3. Mg (Magnesium)
4. B (Boron) - Highest Ionization Potential

### Conclusion
The correct order of their ionization potential is:
**K < Al < Mg < B**