The origin of the word atom comes from the Greek and means indivisible. The concept of indivisible comes from the first atomic model of Democritus in which the atom was believed to be the smallest element that could exist. However, today we know that the atom is made up of other, even smaller particles.
All atoms of any element contain protons, neutrons, and electrons, with the exception of hydrogen-1 and the hydrogen cation. In this case, hydrogen-1 does not contain neutrons, and the hydrogen or hydron cation does not contain electrons.
Protons and neutrons make up the atomic nucleus. These types of subatomic particles are called nucleons, as they are part of the atomic nucleus.
Electrons and protons are commonly used in particle accelerators
The Electron, the Smallest Subatomic Particle
Electrons orbit around the atomic nucleus. The electron is the lightest of the three particles that make up the atom.
The electron has a negative electric charge and is defined as the elemental electric charge. Currently it is unknown if it has a substructure, so it is considered an elemental particle.
The Proton, the Particle That Defines a Chemical Element
The mass of a proton is 1836 times the mass of the electron and it has a positive charge.
Neutron, the Negatively Charged Nucleon
The neutron has a mass very similar to that of the proton but slightly less. The neutron has a neutral electrical charge (neither positive nor negative).
Outside the atomic nucleus, neutrons are not stable and their half-life is less than 15 minutes.
The neutron was the last subparticle of the atom to be discovered. The discoverer was James Chadwick as early as the 20th century.
What Are Quarks?
A quark is a type of elementary particle and a fundamental constituent of matter. All commonly observable matter is made up of quarks and electrons.
The proton and neutron are not elementary particles, but are a composite of other particles called quarks.