One of the surprises of modern science is that atoms and sub-atomic particles do not behave like anything we see in the everyday world. They are not small balls that bounce around; they have wave properties. The Standard Model theory can mathematically describe all the characteristics and interactions that we see for these particles, but our everyday intuition will not help us on that tiny scale.

Physicists use the word "quantum," which means "broken into increments or parcels," to describe the physics of very small particles. This is because certain properties only take on discrete values. For example, you can only find electric charges that are an integer multiples of the electron's charge (or 1/3 and 2/3 for quarks). Quantum mechanics describes particle interactions.

A few of the important quantum numbers of particles are:

Electric charge. Quarks may have 2/3 or 1/3 electron charges, but they only form composite particles with integer electric charge. All particles other than quarks have integer multiples of the electron's charge.

Color charge. A quark carries one of three color charges and a gluon carries one of eight color-anticolor charges. All other particles are color neutral.

Flavor. Flavor distinguishes quarks (and leptons) from one another.

Spin. Spin is a bizarre but important physical quantity. Large objects like planets or marbles may have angular momentum and a magnetic field because they spin. Since particles also to appear to have their own angular momentum and tiny magnetic moments, physicists called this particle property spin. This is a misleading term since particles are not actually "spinning." Spin is quantized to units of 0, 1/2, 1, 3/2 (times Planck's Constant, ) and so on.