Neil Bohr is the one that came up with this theory. 
* Electrons revolve around the nucleus in fixed circular path call orbits 
* the electron can travel indefinitely within an energy level without loosing energy 
* every orbit has a definite energy 
* the orbit shells further away from the nucleus have high energy 
* Electrons in lower orbit can absorb energy and move to a higher orbit, these electrons are known as excited electrons 
* these excited state electrons can come to the ground state by emitting the additional energy it possesses.
1. The atom is neutral. 
2. The protons in a nucleus should only repel each other 
3.The electrons in the nucleus would push apart the protons. 
4.We can see clear evidence of another force in the world around us.
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