Amongst the following elements, the highest ionization energy is : — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

Step 1: Identify the elements: (a) Al, (b) P, (c) Si, and (d) As. Both P and As have half-filled p^3 configurations, which are exceptionally stable. Step 2: Compare P (3rd period) and As (4th period). Ionization energy decreases down a group as atomic size increases and valence electrons are further from the nucleus. Step 3: Since Phosphorus (P) is smaller than Arsenic (As), its outer electrons are held more tightly, giving [Ne] 3s^2 3p^3 the highest ionization energy.