For a ion, the exact ratio of the radius of the 2nd Bohr orbit to the 5th Bohr orbit () will be: — Atomic Structure Chemistry Question

💡 Solution & Explanation

The radius of the $n^{th}$ Bohr orbit is directly proportional to $n^2$ ($r \propto n^2/Z$). For the same ion ($Z=3$), the ratio $r_2 : r_5 = 2^2 : 5^2 = 4 : 25$.