Written by the Fiveable Content Team • Last updated September 2025
Verified for the 2026 exam
Verified for the 2026 exam•Written by the Fiveable Content Team • Last updated September 2025
Definition
The atomic number of an element is the number of protons in the nucleus of an atom. It defines the chemical properties of the element and its place in the periodic table.
Related terms
Proton: A proton is a subatomic particle found in the nucleus of every atom. It carries a positive electric charge.
Electron: An electron is a subatomic particle that orbits around the nucleus and carries a negative electric charge.
Neutron: A neutron is another type of subatomic particle found in the nucleus. It carries no electrical charge and its mass is slightly larger than that of a proton.