What is an atom made of?
An atom is made of a tiny, dense nucleus containing protons and neutrons, surrounded by electrons. Protons and neutrons are themselves made of smaller particles called quarks.
Protons carry a positive electric charge, electrons carry a negative charge and neutrons have no charge. The number of protons decides which element an atom is. Hydrogen has one proton, carbon has six and gold has 79. In a neutral atom, the number of electrons equals the number of protons.
Almost all of an atom's mass is in the nucleus, but the nucleus is incredibly small. If an atom were the size of a football stadium, the nucleus would be about the size of a pea in the center. The rest is mostly empty space where electrons move in regions called orbitals.
Even smaller pieces
Each proton and neutron contains three quarks held together by the strong nuclear force, carried by particles called gluons. Electrons, as far as scientists know, are not made of anything smaller. These particles and forces are described by a theory called the Standard Model of particle physics.
Did You Know?
The word atom comes from the Greek atomos, meaning uncuttable. Ancient Greek thinkers such as Democritus believed matter was made of tiny particles that could not be divided.