Question

Arrange the following elements in the increasing order of their atomic radii.
Hydrogen, potassium, sodium, lithium

• A. Hydrogen < potassium < sodium < lithium
• B. Potassium < sodium < lithium < hydrogen
• C. Hydrogen < lithium < sodium < potassium
• D. Potassium < hydrogen < lithium < sodium

Answer 1

The correct option is C Hydrogen < lithium < sodium < potassium

The given elements belongs to same group (1st group) of the modern periodic table. While going from top to bottom within any group, one electronic shell gets addded. So, the distance between the nucleus and outermost shell increases down the group and hence the atomic radius also increases.
Thus the correct order of elements in the increasing order of their atomic radii is given below:
hydrogen < lithium < sodium < potassium