Which state of triply ionised Beryllium `(Be^(+++))` the same orbital radius as that of the ground state hydrogen ?

Answer

2

Explanation

For H-like particles, `r_n = 0529xx n^2/Z`
For ground state of H-atom, Z = 1, n = 1, `r_1 = 0.529 Å`
For `Be^(3+)` (Z = 4), if `n^(th)` orbit has the same radius, then `0.529xx n^2/4 = 0.529` or `n^2 = 4` i.e. n = 2
Thus, second orbit of `Be^(3+)` ion has same radius as that of ground state (1st orbit) of H-atom.