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

💡 Solution & Explanation

# Ionization Potential Trend in a Period **Step 1: Recall the definition** Ionization potential (IP) is the energy required to remove an electron from an atom. Lower IP means easier electron removal. **Step 2: Identify the trend across a period** Moving left to right across a period: - Nuclear charge increases - Electrons are added to the same shell - Effective nuclear charge increases - Electrons are held more tightly **Step 3: Recognize the exception** Despite the general increasing trend, **alkali metals (Group 1)** have anomalously LOW ionization potentials because: - They have a single valence electron in their outermost $s$-orbital - This electron is far from the nucleus and shielded by inner electrons - Removing this electron gives a stable noble gas configuration **Step 4: Compare with other elements** - Group 2 (alkaline earth metals): Slightly higher IP than Group 1 - Transition metals and main group elements: Much higher IP - Halogens: Very high IP (nearly complete valence shell) **Conclusion:** The **leftmost element in each period** (alkali metals of Group 1) shows the **lowest ionization potential** because the valence electron is most loosely bound and easiest to remove. *Note: Option C likely refers to Group 1/alkali metals or the leftmost position in a period.*