Protons
Protons are positively-charged particles that are part of the nucleus of an atom.

Neutrons
Neutrons are electrically-neutral particles that are part of the nucleus of an atom.

Nucleons
Nucleons are particles that form the nucleus of an atom. Protons and neutrons are nucleons.

Fundamental particles
Fundamental particles are particles of matter that cannot be divided into smaller particles.

Strong Nuclear Force
The Strong Nuclear Force is force holds that holds protons and neutrons very tightly together to form an atom’s nucleus. It is also called “chromoelectric” force, because the gluons that carry it have an assigned characteristic called “color.”

Color
The color of a quark refers to the type of strong nuclear forces that hold quarks tightly to each other. These forces are assigned colors of red, green or blue.

Flavor
The flavor of a quark designates the kind or the variety of a quark. For example, there are “up” quarks and “down” quarks.

Elementary Charge
An elementary charge is the negative charge carried by a single electron. A proton carries an equivalent, but positive, charge.

Alpha Particles
Alpha particles are positively charged particles ejected at high speeds from some radioactive substances. They contain the same nucleons as a helium nucleus—two protons and two neutrons.

Gluons
Gluons are massless carriers of the strong nuclear force. They have assigned red, green or blue “ color.”