Lowest ionization potential in periods is shown by — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

# Ionization Potential Trend in Periods **Step 1: Understand Ionization Potential** Ionization potential (IP) is the energy required to remove an electron from an atom. Lower IP means the electron is easier to remove. **Step 2: Analyze Periodic Trend** Across a period (left to right): - Nuclear charge increases - Electrons are added to the same shell - Atomic radius decreases - Electrons are held more tightly → IP increases **Step 3: Identify the Exception** The lowest IP in any period occurs at the **leftmost element of that period** — specifically the **alkali metals (Group 1)**. Alkali metals have: - Only 1 valence electron in the outermost shell - Largest atomic radius in the period - Weakest hold on the valence electron - Lowest ionization energy **Step 4: Conclusion** The correct answer is **C: Alkali metals (or Group 1/IA elements)** Examples: Li, Na, K, Rb, Cs show the lowest IP values in their respective periods because their single valence electron is furthest from the nucleus and easiest to remove.