Question

Bohr's theory is not applicable to :

• A. He
• B. Li${}^{2+}$
• C. He${}^{2+}$
• D. H-atom

Answer 1

Answer: (A), (C)

The correct options are
A He
C He${}^{2+}$

Bohr's theory is applicable to hydrogen like atoms (single electron system).
Here, Li${}^{2+}$ and H-atom consists of only one electron. He, He${}^{2+}$ consists of 2, 0 electrons, respectively.
Hence, options A & C are correct.