Question

The ionisation energy of B and Al as compared to Be and Mg are :

• A. lower
• B. higher
• C. equal
• D. none of these

Answer 1

The correct option is A lower

The ionization energies of B and Al as compared to Be and Mg are lower.
The electronic configurations of Be and B are $1s^{2}2s^2$ and $1s^{2}2s^{2}2p^1$. When an electron is removed from Be, the stable configuration of completely filled 2s orbital is broken. When an electron is removed from B, the stable configuration of completely filled 2s orbital is obtained.
The valence shell electron configurations of Mg and Al are $3s^2$ and $3s^{2}3p^1$.
When an electron is removed from Mg, the stable configuration of completely filled 3s orbital is broken and when electron is removed from Al, the stable configuration of 3s orbital is obtained.