What is the best description of an bohr model of an atom?

Answer 1

Each electron in an atom is in an orbital (*NOT* an orbit!!) at a specific energy level from the positive nucleus. The energy levels of these orbitals are fixed -- an electron can go from orbital 's' to orbital 'p', but it can't go halfway between these two orbitals. When an electron in an atom goes from a higher orbital to a lower one, then the atom must give off an amount of energy, that is exactly the difference in energy in the two levels.

For a hydrogen atom, these orbital levels are fixed by the fact that the angular momentum of an electron in an orbital is quantized -- ie, it comes in exact multiples, but not fractions, of a minimal amount.