To determine which element has the maximum second ionization energy among Boron (B), Beryllium (Be), Magnesium (Mg), and Aluminium (Al), we can follow these steps:
### Step 1: Understand Ionization Energy
Ionization energy is the energy required to remove an electron from an atom. The first ionization energy is the energy needed to remove the first electron, while the second ionization energy is the energy needed to remove a second electron after the first has been removed.
### Step 2: Write Electron Configurations
We need to write the electron configurations for each of the elements:
- **Boron (B)**: Atomic number 5 → Electron configuration: 1s² 2s² 2p¹
- **Beryllium (Be)**: Atomic number 4 → Electron configuration: 1s² 2s²
- **Magnesium (Mg)**: Atomic number 12 → Electron configuration: 1s² 2s² 2p⁶ 3s²
- **Aluminium (Al)**: Atomic number 13 → Electron configuration: 1s² 2s² 2p⁶ 3s² 3p¹
### Step 3: Analyze the Second Ionization Energy
To find the second ionization energy, we need to consider what happens after the first electron is removed:
- For **Beryllium (Be)**, after removing one electron, it becomes Be⁺ (1s²), which has a stable electron configuration. The second ionization energy will be relatively high because removing an electron from a filled shell requires more energy.
- For **Boron (B)**, after removing one electron, it becomes B⁺ (1s² 2s² 2p⁰). The second ionization energy will be lower than that of Beryllium because it is easier to remove an electron from a half-filled p subshell.
- For **Magnesium (Mg)**, after removing one electron, it becomes Mg⁺ (1s² 2s² 2p⁶ 3s¹). The second ionization energy will be lower than that of Beryllium because it is easier to remove an electron from the 3s subshell.
- For **Aluminium (Al)**, after removing one electron, it becomes Al⁺ (1s² 2s² 2p⁶ 3s² 3p⁰). Similar to Boron, the second ionization energy will be lower than that of Beryllium.
### Step 4: Compare the Second Ionization Energies
From the analysis:
- Beryllium has a filled outer shell after the first ionization, making its second ionization energy the highest.
- Boron, Magnesium, and Aluminium have less stable configurations after the first ionization, resulting in lower second ionization energies compared to Beryllium.
### Conclusion
The element with the maximum second ionization energy is **Beryllium (Be)**.
