Question

Among the elements Li, K, Ca, Sr and Kr which one has the lowest atomic radius and which one has the highest?

Answer 1

Step-1: Introduction

Atomic radii is distance of the electrons in the outermost from the atomic nucleus. It increases from top to bottom in a group and decreases from left to right in a period but is highest for a noble gas.

Step-2: Arrangement of elements into groups and periods

Lithium ($\mathrm{Li}$) and Potassium ($\mathrm{K}$) belongs to group 1. Calcium ($\mathrm{Ca}$) and Strontium ($\mathrm{Sr}$) belongs to group 2 whereas Krypton ($\mathrm{Kr}$) belongs to group 18. But Calcium and Krypton belongs to same period 4.

Since Krypton is a noble gas, it has the highest atomic radii compared to other elements.

Lithium is a small element that contains 2 electrons in K-shell and 1 electron in L-shell. So, the distance in between outermost L-shell and the nucleus is small. But in the case of elements like Potassium, Calcium and Strontium, they contains K-shell, L-shell and M-shell thereby the atomic size increases.

Final answer

Therefore, Lithium has the lowest atomic radius and Krypton has the highest atomic radius.