The Online Library of Knowledge


Subatomic particles

Subatomic particles inside an atomSubatomic particles inside an atom An atom is the smallest part of an element. But an atom is not the smallest thing there is. Inside it are even smaller, subatomic particles. Most of these cluster together in the tiny nucleus at the centre of the atom: protons and neutrons (the other subatomic particles are electrons, which orbit the nucleus). A very powerful force keeps these two kinds of particles together. It is called the strong nuclear force and operates at the tiny distances found within the nucleus. When atomic nuclei collide and join, or fuse, together, as happens inside the Sun, massive amounts of energy are either released or absorbed. Energy can also be released when atomic nuclei are split apart (nuclear fission), as happens in nuclear power stations.

The structure of a protonThe structure of a proton


Incredibly, protons and neutrons are themselves formed from still smaller particles, called quarks. Protons and neutrons both contain three quarks, but they contain a different balance of two kinds of quark, known as “up” or “down”. Neutrons contain one up quark and two down quarks, while protons contain two up quarks and one down quark. Protons can readily change into neutrons, and vice versa, by changing one of their quarks. The quarks are held together by other types of subatomic particles, called gluons. But unlike larger subatomic particles like protons, quarks and gluons cannot exist on their own.
Particle tracks, created by high-speed collisionsParticle tracks, created by high-speed collisions

Higgs boson

Protons are about 2000 times heavier than electrons.

© 2020 Q-files Ltd. All rights reserved. Switch to Mobile