The second ionization energy is maximum for:

Options

A. Boron
B. beryllium has a lower nuclear charge than boron
C. magnesium
D. aluminium

Answer

To determine which element has the maximum second ionization energy among boron (B), beryllium (Be), magnesium (Mg), and aluminum (Al), we need to analyze the electronic configurations of these elements after the removal of one electron and then assess the stability of the resulting ions.

### Step-by-Step Solution:

1. **Identify the Atomic Numbers and Electronic Configurations:**
- Boron (B) has an atomic number of 5:
- Electronic configuration: 1s² 2s² 2p¹
- Beryllium (Be) has an atomic number of 4:
- Electronic configuration: 1s² 2s²
- Magnesium (Mg) has an atomic number of 12:
- Electronic configuration: 1s² 2s² 2p⁶ 3s²
- Aluminum (Al) has an atomic number of 13:
- Electronic configuration: 1s² 2s² 2p⁶ 3s² 3p¹

2. **Remove One Electron to Find the First Ionization Energy:**
- For Boron (B):
- B → B⁺: 1s² 2s² 2p⁰ (removing one 2p electron)
- For Beryllium (Be):
- Be → Be⁺: 1s² 2s¹ (removing one 2s electron)
- For Magnesium (Mg):
- Mg → Mg⁺: 1s² 2s² 2p⁶ 3s¹ (removing one 3s electron)
- For Aluminum (Al):
- Al → Al⁺: 1s² 2s² 2p⁶ 3s² 3p⁰ (removing one 3p electron)

3. **Determine the Electronic Configurations After the Second Ionization:**
- For B⁺:
- B⁺ → B²⁺: 1s² 2s² (removing one electron from a stable configuration)
- For Be⁺:
- Be⁺ → Be²⁺: 1s² (removing the last 2s electron)
- For Mg⁺:
- Mg⁺ → Mg²⁺: 1s² 2s² 2p⁶ (removing the last 3s electron)
- For Al⁺:
- Al⁺ → Al²⁺: 1s² 2s² 2p⁶ 3s² (removing one of the 3s electrons)

4. **Analyze the Stability of the Resulting Configurations:**
- B²⁺ has a stable configuration (1s² 2s²), but it is still relatively stable.
- Be²⁺ has a completely filled 1s² configuration, which is very stable.
- Mg²⁺ has a noble gas configuration (1s² 2s² 2p⁶), which is highly stable.
- Al²⁺ also has a noble gas configuration (1s² 2s² 2p⁶ 3s²), but it is less stable than Mg²⁺ due to the additional energy levels.

5. **Conclusion:**
- The second ionization energy is highest for B²⁺ because removing an electron from a stable filled configuration (1s² 2s²) requires a significant amount of energy.
- Therefore, the element with the maximum second ionization energy is **Boron (B)**.

### Final Answer:
The second ionization energy is maximum for **Boron (B)**.