Question

A hydrogen atom, unipositive helium, dipositive lithium contain single electron in the same shell. The radius of the shell:

• A. decreases
• B. increases
• C. remains unaffected
• D. cannot be predicted

Answer 1

The correct option is A decreases

radius of $n^{th}$ orbit of single elctron system is:

$r\propto \frac{n^2}{Z}$

$\therefore r_H:r_{H{e}^{+}}:r_{L{i}^{2+}}::\frac{1}{1}:\frac{1}{2}:\frac{1}{3}$

it decreases as $6:3:2$

A is correct