Elements Z = 117 and 120 have not yet been discovered. In which family/group would you place these elements and also give electronic configuration in each case. NCERT Intext 3.3 Question Solution

Anand Classes provides the detailed NCERT Intext 3.3 solution for Class 11 Chemistry: The elements Z = 117 and 120 have not yet been discovered. In which family/group would you place these elements and also give the electronic configuration in each case? The solution explains how Z = 117 belongs to the halogen family (Group 17) with configuration [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁵, and Z = 120 belongs to the alkaline earth metals (Group 2) with configuration [Uuo] 8s². This explanation is important for JEE, NEET, and CBSE students to understand periodic table predictions. Click the print button to download study material and notes.

❓ Question

The elements Z = 117 and 120 have not yet been discovered. In which family/group would you place these elements and also give the electronic configuration in each case.

✅ Solution with Explanation

1. Element with Atomic Number Z = 117
   • Position: From the periodic table trends, Z = 117 lies in Group 17 → the halogen family.
   • Reason: Group 17 elements have the general electronic configuration ns²np⁵, i.e., they end with 7 valence electrons.
   • Expected Electronic Configuration: [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁵
   • Thus, element 117 will behave like a halogen (similar to Iodine and Astatine).

2. Element with Atomic Number Z = 120
   • Position: From the periodic table extension, Z = 120 will lie in Group 2 → the alkaline earth metals.
   • Reason: Group 2 elements have the general electronic configuration ns², i.e., they end with 2 valence electrons.
   • Expected Electronic Configuration: [Uuo] 8s² where [Uuo] represents the noble gas with Z = 118 (Oganesson).
   • Hence, element 120 would resemble Calcium, Strontium, Barium, and Radium in its chemical behavior.

🔑 Final Answer

• Z = 117 → Group 17 (Halogen Family), Configuration: [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁵
• Z = 120 → Group 2 (Alkaline Earth Metal Family), Configuration: [Uuo] 8s²

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