Atomic Structure: Practice Problem & Solution

Solution Explained:

To solve this problem, we apply the core principles of Atomic Structure. Understanding the underlying formula is key to arriving at the correct answer below:

The radius of the nth Bohr orbit is $r_n = r_0 n^2$, where $r_0$ is the Bohr radius. For the first excited level ($n=2$), $r_2 = r_0(2^2) = 4r_0$. Hence, it is 4 times the Bohr radius.