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" of "Li^(2+)=3`
`r_(n)=(0.529xxn^(2))/(Z)Å"        "(r_(1))/(r_(2))=(Z_(2))/(Z_(1))=(3)/(2) or 3:2`