The simple Bohr model is not applicable to He4 atom because (a) He4 is an inert gas (b) He4 has neutrons in the nucleus (c) He4 has one more electron (d) electrons are not subject to central forces
Correct options are C) and D) Bohr's atomic model is applicable only for one electron species and in He4 there are two electrons. Electrons are not subject to central forces due to longer distance than nuclear size
