What is the ratio of the radii of the 3rd orbits of `He^(+)` and `Li^(2+)` ?

Explanation

n is constant and its value is 3.
Z of `He^(+) = 2`, Z = `Li^(2+) = 3`
`r_(n) = (0.529 xx n^(2))/(Z)Å " "(r_(1))/(r_(2)) = (Z_(2))/(Z_(1)) = (3)/(2)` or 3:2