Proton

Definition

A proton is a subatomic particle found in the nucleus of an atom, carrying a positive electric charge. Protons contribute to the atomic number and define the element.

5 Must Know Facts For Your Next Test

1. Protons have a positive charge of +1e, where e is the elementary charge.
2. The number of protons in an atom's nucleus determines the element's atomic number.
3. Protons are composed of three quarks: two up quarks and one down quark.
4. The mass of a proton is approximately 1.67 x 10^-27 kilograms, slightly less than that of a neutron.
5. In neutral atoms, the number of protons equals the number of electrons.

Review Questions

• What is the charge and location of a proton within an atom?
• How does the number of protons in an atom’s nucleus relate to its atomic number?
• What particles make up a proton?

Related terms

Neutron:

A subatomic particle found in the nucleus with no electric charge and a mass slightly greater than that of a proton.

Electron:

A subatomic particle with a negative charge found in orbitals around the nucleus.

Atomic Number:

The number of protons in an atom's nucleus, which uniquely identifies an element.