Which of the following anion has the smallest radius? — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

Step 1: Compare the ionic radii of H-, F-, Cl-, and Br-. Step 2: Going down the halogen group (F- to Br-), size increases: F- < Cl- < Br-. The hydride ion (H-) has only 1 proton to hold 2 electrons, which leads to weak nuclear hold and a relatively large radius (around 140 pm), which is larger than F- (~133 pm). Step 3: Thus, F- has the smallest radius among the given anions, corresponding to option (b).