Q 12-12-009NEETNEET 2020Top questionEasy
For which one of the following, Bohr model is not valid ?
Answer: (D) Singly ionised neon atom (Ne$^+$)
Concept. Bohr's model treats a single electron in the field of a nucleus, so it holds only for one-electron (hydrogen-like) systems.
Step 1. Count electrons. H, deuterium and He$^+$ each have one electron. Ne$^+$ ($Z = 10$) still has $9$ electrons, so the model does not apply.
Answer. Singly ionised neon (Ne$^+$) (Option D).
Solution by Sreeraj P, M.Sc Physics