Final answer:
The Bohr model assumes electrons orbit the nucleus in fixed orbits with quantized angular momentum, and that energy is emitted or absorbed only during transitions between these orbits. The force that holds the electrons in orbit is electrostatic attraction. It does not include elliptical orbits nor does it state there is only one electron or proton.
Step-by-step explanation:
The Bohr model of the atom, developed by Niels Bohr, makes several fundamental assumptions about the structure of atoms. According to Bohr's model, one of the key assumptions is that the electron orbits the nucleus in specific allowable paths called orbits, with fixed energies. Therefore, only certain values of angular momentum are allowed, and these are quantized according to the formula Ln = nħ, where n is the principal quantum number representing different energy levels. The force between the electron and the nucleus is electrostatic attraction, not repulsive. In a stationary state, the atom indeed does not lose energy, but it certainly can gain or lose energy when transitioning between different energy levels, leading to the absorption or emission of a photon.
One of the assumptions that are not part of Bohr's model is the idea of elliptical orbits; Bohr assumed only circular orbits. Also, the model does not assume there is only one electron or one proton, although it was primarily developed to explain the hydrogen atom, which has one electron and one proton. Since other elements have more complex electron configurations, Bohr's model is less accurate for them.