The corresponding I states for different values of n look very much the same, except that they increase in size as n increases. Because we cannot know the exact path of the electron, these electron probability clouds should not be called orbits, but the similarity to the older theory is maintained by calling them orbitals. Every allowed combination of n, l, and m describes an atomic orbital of a certain shape and energy.

All s (or I =0) orbitals - 1s, 2s, 3s, 4s, or higher - are spherical (see opposite). The electron in such an orbital has an equal probability of being found in any direction from the nucleus. In contrast, the three p orbitals (I =1), each with a different value of magnetic quantum number m, have maximum electron probabilities in three mutually perpendicular directions, which we can call the x, y, nand z axes. All three are illustrated on the next page. There is no point in trying to associate the orbitals individually with the m values -1, 0, and +1, because all three have the same energy in the absence of an outside magnetic field. The important feature is not the numerical value of m, but the shape and orientation of the orbitals.