Which one of the following is a different pair? — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

Step 1: Analyze the group classification of the elements in each pair in the periodic table. Step 2: Li and Na both belong to Group 1 (alkali metals). Be and Ba both belong to Group 2 (alkaline earth metals). N and As both belong to Group 15 (pnictogens). O belongs to Group 16 (chalcogens) while At belongs to Group 17 (halogens). Step 3: Conclude that O and At belong to different groups, making (d) the different pair.