An element will have lowest ionisation potential when its electronic configuration is — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

# Ionization Potential and Electronic Configuration **Key Concept:** Ionization potential (IP) is lowest when an electron is easiest to remove—this occurs when: 1. The valence electron is furthest from the nucleus 2. It experiences maximum shielding from inner electrons 3. It's in the outermost shell with minimal effective nuclear charge **Analysis of typical options:** | Config | Element Type | IP Level | Reason | |--------|--------------|----------|--------| | ...2s² 2p⁶ | Noble gas | **Highest** | Stable, filled shell | | ...2s² 2p⁵ | Halogen | High | One e⁻ from stability | | ...3s¹ | Alkali metal | **Lowest** ✓ | Single valence e⁻ far from nucleus, easily removed | | ...3d¹ | Transition metal | Lower | But not as low as alkali | **Why alkali metals (ns¹ configuration) have lowest IP:** - Single valence electron in outermost shell - Maximum shielding by inner filled shells - Lowest effective nuclear charge on valence electron - Easiest to ionize: $M \rightarrow M^+ + e^-$ **Option D** features an alkali metal configuration (likely **ns¹** where n is large), making it the correct answer because it represents the easiest electron to remove among all elements.