http://www.answers.com/topic/atomic-orbital
Atomic orbitals are cloud like structures around the nucleus of an atom that contain the atoms electrons. There are s, p, d, and f orbitals. S contain up to 2 electrons, P contain up to 6 electrons, d contain up to 10 electrons, and f contain up to 14 electrons. These orbitals have electrons containing different amounts of energy, and it is possible for electrons to jump to and from different orbitals. When this happen energy either needs to be added or released. The number of orbitals present in an atom is completely dependent on the number of electrons present in the atom.