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.