Proton

Definition

A proton is a subatomic particle found in the nucleus of an atom that carries a positive electric charge. It determines the element's atomic number and contributes to the mass of the atom.

5 Must Know Facts For Your Next Test

1. Protons have a positive charge equal in magnitude but opposite to that of electrons.
2. The number of protons in an atom's nucleus defines the chemical element; for example, hydrogen has one proton.
3. Protons are made up of three quarks held together by strong nuclear forces.
4. The discovery of the proton is attributed to Ernest Rutherford in 1917.
5. Protons, along with neutrons, make up most of an atom's mass.

Review Questions

• What is the charge of a proton?
• Who is credited with discovering the proton?
• How does the number of protons relate to an element’s identity?

Related terms

Neutron: A subatomic particle found in the nucleus of an atom that has no electric charge.

Electron: A subatomic particle with a negative charge that orbits the nucleus of an atom.

AtomicNumber: The number of protons in the nucleus of an atom, which determines its chemical properties and its place in the periodic table.