The basic feature of quantum mechanics that is incorporated in the Bohr Model and that is completely different from the analogous planetary model is that the energy of the particles in the Bohr atom is restricted to certain discrete values. One says that the energy is quantized. This means that only certain orbits with certain radii are allowed; orbits in between simply don't exist. This is illustrated in the adjacent diagram of the energy levels for the hydrogen atom.

For the bound states of hydrogen (below the ionization threshold of 13.6 electron volts (eV), the states are at discrete energies, and there are no states at the energies in between. Although this may seem strange to our minds trained as they are by watching phenomena in the macroscopic world, this is the way things behave in the strange world of the quantum that holds sway at the atomic level.