Question

The radius of electron's second stationary orbit in Bohr's atom is $R$. The radius of $3^{\text{rd}}$ orbit will be

• A. $\frac{R}{3}$
• B. $9R$
• C. $2.25R$
• D. $3R$

Answer 1

Answer: (C)

$r=0.529\times \frac{n^2}{z}$
$r\propto n^2$
$R\propto (2{)}^2$
$R_1\propto (3{)}^2$
Divide (1) by (2) $\frac{R_1}{R}=\frac{4}{9}$
$R_1=\frac{9R}{4}$
$R_1=2.25R$