Question

element whose atoms have three outermost shell incomplete are called

Answer 1

14 elements from atomic number 58 (Cerium) to 71(Lutetium) are called as Lanthanides and the another 14 elements from atomic number 90 (Thorium) to 103(Lawrencium) are called as Actinides. These 28 elements are arranged in the 2 series placed below the Modern Periodic Table and the elements in these 2 series are collectively called as f-block elements. These elements have outermost three shells incomplete

Answer 2

Answer: The elements of lanthanoid and actinoid have 3 incomplete outermost shells.

Explanation: The general electronic configuration of lanthanoid series is

[Xe] 4f¹⁻ ¹⁴ 5d⁰⁻¹6s² so from the electronic configuration it is clear that the last 3 shells are incomplete. Elements with atomic number 58 to 71 are members of this series.

The general electronic configuration of the actinoid series is [Rn] 4f⁰⁻ ¹⁴ 6d⁰⁻²7s². So here is also the last 3 shell of the elements are incomplete. Elements with atomic number 89 to 103 are members of this series.

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