Question

The radius of hydrogen atom, when it is in its second excited state ,becomes $\underset{–}{}$ its ground state radius.

• A. half
• B. double
• C. four times
• D. nine times

Answer 1

The correct option is D nine times

$r=\frac{a_0{n}^2}{Z}$
$r_1$ ( ground state ) $=a_0(1{)}^2$
$=a_0$
$r_2$ ( 2nd excited state ) $=a_0(3{)}^2$
$=9a_0$