Q. The radius of electron in the first excited state of hydrogen atom is (Where, $a_{0}$ is the Bohr’s radius)
A) $a_{0}$
B) $4a_{0}$
C) $2a_{0}$
D) $8a_{0}$
Explanation
(b)
For first excited state ($i.e$., second energy level)
$\ \ \ \ \ \ \ \ \ \ \ \ \ n = 2$
$\ \ \ \ \ \ \ \ \ \ \ r_{n} = \frac{a_{0}.n^{2}}{Z}$
$\ \ \ \ \left( where,\ a_{0} = Bohr\ radius = 0.53\ \mathring{\mathrm{A}} \right)$
$\ \ \ \ \ \ \ \ \ \ \ r_{2} = \frac{a_{0}(2)^{2}}{1}\ \ \ \ \ \ \ \ \ \ \ \ \ \ (for\ H,Z = 1)$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = 4a_{0}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.