What is the ratio of the radius of the third stationary orbit of a Li ²⁺ ion to that of a He ⁺ ion?

Step-by-step solution

According to Bohr's model, the radius of the n^ th stationary orbit of a hydrogen-like species is given by: r_n n^2 Z For the third stationary orbit, n = 3 is constant for both ions. Thus, the radius is inversely proportional to the atomic number Z . r 1 Z For Li ²⁺ , Z = 3 . For He ⁺ , Z = 2 . The ratio of their radii is: r_ Li ²⁺ r_ He ⁺ = Z_ He ⁺ Z_ Li ²⁺ = 2 3 Therefore, the required ratio is 2:3 . Answer: 2:3