Question

On the basis of Bohr's atomic model, the radius of the $3rd$ orbit is______.

• A. equal to the radius of first orbit
• B. three times to the radius of first orbit
• C. five times to the radius of first orbit
• D. nine times to the radius of first orbit

Answer 1

The correct option is D nine times to the radius of first orbit

Bohr radius of the hydrogen atom is the first orbit in the hydrogen atom.

And we know $r=a_0\frac{n^2}{z}$

So $\frac{r_3}{r_1}=\frac{3^2}{1^2}=\frac{9}{1}$

or $r_3=9r_1$

Hence, option D is correct.