Proton

atoms · physics · building blocks

Heart of atoms. Protons live in the nucleus, the dense center of an atom. Every atom has at least one proton, and the number of protons determines what element an atom is (hydrogen has 1, carbon has 6, gold has 79).

Positive charge. Protons carry a positive electric charge. This positive charge is what attracts electrons, which have negative charges, to form atoms and hold them together.

Nearly neutron-sized. A proton weighs almost exactly the same as a neutron, and scientists group them together as nucleons. Both are about 1,836 times heavier than a single electron.

Incredibly stable. Protons last forever and never decay, which is why they are so reliable as building blocks of matter. This stability is one of the reasons the universe can exist as we know it.