<P> The unbalanced spin creates spin magnetic moment, making the electron act like a very small magnet . As the atoms pass through the in - homogeneous magnetic field, the force moment in the magnetic field influences the electron's dipole until its position matches the direction of the stronger field . The atom would then be pulled toward or away from the stronger magnetic field a specific amount, depending on the value of the valence electron's spin . When the spin of the electron is + 1 / 2 the atom moves away from the stronger field, and when the spin is − 1 / 2 the atom moves toward it . Thus the beam of silver atoms is split while traveling through the in - homogeneous magnetic field, according to the spin of each atom's valence electron . </P> <P> In 1927 Phipps and Taylor conducted a similar experiment, using atoms of hydrogen with similar results . Later scientists conducted experiments using other atoms that have only one electron in their valence shell: (copper, gold, sodium, potassium). Every time there two lines formed on the metallic plate . </P> <P> The atomic nucleus also may have spin, but protons and neutrons are much heavier than electrons (about 1836 times), and the magnetic dipole moment is inversely proportional to the mass . So the nuclear magnetic dipole momentum is much smaller than that of the whole atom . This small magnetic dipole was later measured by Stern, Frisch and Easterman . </P> <P> In 1928, Paul Dirac developed a relativistic wave equation, now termed the Dirac equation, which predicted the spin magnetic moment correctly, and at the same time treated the electron as a point - like particle . Solving the Dirac equation for the energy levels of an electron in the hydrogen atom, all four quantum numbers including s occurred naturally and agreed well with experiment . </P>

The symbol for the spin magnetic quantum number is