In quantum mechanics, a branch of physics, the Bohr model is the model of the atom set forth by Neils Bohr. Bohr's model is useful only when discussing the behavior of a hydrogen atom. Bohr's model is extremely useful in describing the hydrogen emission spectrum.
Energy Levels [change]
The Bohr model says that the various energy levels that an electron might be found on within a hydrogen atom can only be multiples of a certain formula. The formula is
Where h is Planck's constant, π is pi, and n is the multiples (1,2,3,...). This formula says that an electron will only be found on the energy levels predicted by the formula; not anywhere in between. This means that if an electron jumps from one energy level to the next, it will never be in between energy levels, but it will instantaneously be transported from one level to the other.
Bohr's model is also useful in that it explains the cause of light. Bohr agreed with classical theory that light has a wave-particle duality (meaning it is made of both electromagnetic waves and particles called photons), but he said that light was given off when an electron in a hydrogen atom jumps from a higher energy level to a lower one. Basically, if an electron with x amount of energy goes to a lower state of energy and loses y energy, then a photon with energy y is emitted by the atom and either becomes light or some other form of radiation.