First electron affinity of all elements is positive. — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

Step 1: Relate the atomic numbers to the nearest noble gases in the periodic table. Radon (Rn) has Z=86, and the 7th period ends with the noble gas Oganesson (Og) at Z=118 in Group 18. Step 2: The element with atomic number Z=117 lies immediately before Oganesson (Z=118) in the 7th period, which places it in Group 17 (the halogens). Step 3: The element with atomic number Z=120 will belong to the 8th period. The alkali metal of Group 1 will be Z=119, and the alkaline earth metal of Group 2 will be Z=120. Thus, they belong to groups 17 and 2.