6The Planetary Model of an Atom 6He chose hydrogen because its atoms are the simplest, having only one electron about the nucleus, and because it produces the simplest spectrum with the fewest lines. According to him, electrons revolve around the nucleus, following fixed paths, or orbits, much as a planet moves around the sun.With his model, Bohr explained how electrons could jump from one orbit to another only by emitting or absorbing energy in fixed quanta. If an electron jumps one orbit closer to the nucleus, it must emit energy equal to the difference of the energies of the two orbits.This theory is called the Planetary Model of an Atom and this is the basis of todays model of an atom.The atomic theory of Niels Bohr, a Danish physicist introduced substantial improvements to the Rutherford model by incorporating energy aspects derived from Planck energy and from Einstein's photoelectric effect.Niels Bohr, a Danish physicist, proposed a theoretical model for the hydrogen atom.