QuestionPeriodic properties / ionisation energy
Which one among the following elements has the highest second ionization potential?
- (a) B
- (b) Be
- (c) Mg
- (d) Al
Answer: (a) B
IE₂ removes an electron from the cation. B⁺ = 1s² 2s² (stable filled 2s, small size) → IE₂ ≈ 25.2 eV. Be⁺ (2s¹) ≈ 18.2, Al⁺ (3s²) ≈ 18.8, Mg⁺ (3s¹) ≈ 15.0 eV → B highest → (a).