Chemistry

Question Analysis
This question involves comparing second ionization energies of Period 3 cations. The main focus is on linking cation electron configuration to the ease of removing an additional electron.

Key Concept Explanation
Second ionization energy for a cation (X⁺) is the energy required to form X²⁺. The energy depends on the stability of the X⁺ electron configuration: electrons in higher-energy orbitals or unpaired electrons are easier to remove than those in filled, stable orbitals.

Step-by-Step Solution
1. Analyze the electron configuration of each cation and the electron to be removed for the second ionization:
A: B: Mg⁺ has an unpaired 3s¹ electron; this electron is in a valence orbital and unpaired, making it relatively easy to remove. D: Si⁺ has a 3p¹ electron; p-orbitals are higher in energy than s-orbitals, but the unpaired s-electron in Mg⁺ is still easier to remove.
Na⁺ ([Ne]) → Removing the second electron means taking it from a full core ([Ne]) → extremely high energy.
B. Mg⁺ ([Ne]3s¹) → Remove the single 3s¹ valence electron ...