As we learned earlier, angular momentum is quantized in quantum mechanics. We can simultaneously measure only the magnitude of the angular momentum vector and one component, usually taken to be the component. Measurement of the other two components simultaneously with the component is forbidden by the uncertainty principle. The magnitude of the orbital angular momentum of an object can take on the values where . The component can likewise equal where .
Particles can have an intrinsic spin angular momentum as well as an orbital angular momentum.
The possible values for the magnitude of the spin angular momentum are and the component of the spin angular momentum where . Spin is an intrinsic, unchangeable quantity for an elementary particle. Fermions can only be created or destroyed in particle-antiparticle pairs, whereas bosons can be created or destroyed singly.