3.Bohr's theory Three major assumptions of Bohr's theory DAn electron in an atom could be located only in certain orbits that have particular radii and energies; 2Usually,an electron would remain in the orbit which is the most close to the nucleus.The atom is said to be in its ground state under this condition,which corresponds to the most stable energy state;Energy absorbed by the atom causes the electron to move from the orbits close to the nucleus to those far from it,then the atom is said to be in an excited state.3.Bohr’s theory Three major assumptions of Bohr’s theory ： ①An electron in an atom could be located only in certain orbits that have particular radii and energies； ②Usually, an electron would remain in the orbit which is the most close to the nucleus. The atom is said to be in its ground state under this condition, which corresponds to the most stable energy state; Energy absorbed by the atom causes the electron to move from the orbits close to the nucleus to those far from it, then the atom is said to be in an excited state