Question

First Bohr radius of an atom with $Z=82$ is $R$. Radius of its third orbit is

• A. 9 R
• B. 6 R
• C. 3 R
• D. R

Answer 1

Answer: (A)

Radius of Bohr's orbit.
$R_n=\frac{A_0{n}^2}{Z}$
$\Rightarrow R_n\propto n^2$ (Z= constant)
$\therefore R_3=3^{2}R=9R$