From quantization of angular momentum, one gets for hydrogen atom. the radius of the `n^(th)` orbit as `r_(n) = (n^(2))/(m_(e)) ((h)/(2 pi))^(2) ((4 pi^(2) epsilon_(0))/(e^(2)) ) ` for a hydrogen like atom of atomic number 'Z'.

Answer

3

Explanation

`Psi^2 = 0 implies 27 - (18 r)/(a_0) - (18)/(a_0) + (2r^2)/(a_0^2) = 0 , (d)/(1.73 a_0) = 3`