The nuclear spin of atoms can be determined by sophisticated improvements to the original Stern-Gerlach experiment. A single-energy (monochromatic) molecular beam of atoms in an inhomogeneous magnetic field will split into beams representing each possible spin quantum state. For an atom with electronic spin S and nuclear spin I, there are (2 S + 1)(2 I + 1) spin states. For example, neutral Na atoms, which have S = 1/2, were passed through a series of inhomogeneous magnetic fields that selected one of the two electronic spin states and separated the nuclear spin states, from which four beams were observed. Thus, the nuclear spin for Na atoms was found to be I = 3/2.