Nuclear spin

Spin is an intrinsic property of electrons, protons and neutrons describing the particles angular momentum. There are two different spin states: 1/2 and -1/2. In most atoms, the total spin is equal to 0 because the different spin states cancel each other out. Only isotopes that have an odd number of protons/neutrons have nonzero spins and are active in NMR experiments such as 13C, 1H, and 15N.