What matter is not composed of atoms?

1. Plasma - Very hot matter where atoms break down to electrons and ions. Stars are in the plasma state. Other examples are supernova remnants, shock-ionized regions, HII regions (regions surrounding a very hot star ionized by radiation), matter surrounding a black hole/neutron star etc. 2. read more

5. Primordial 'matter' - Shortly after the big bang, the matter/energy was so hot that there was no distinction between matter and radiation. Obviously, atoms could not have existed back then or for a very long time after that because of the high temperature. read more

Learn about the structure of the atom, and how atoms make up matter. An atom is the smallest unit of matter that retains all of the chemical properties of an element. If you're seeing this message, it means we're having trouble loading external resources on our website. read more

The Atom . Dalton's Atomic Theory (1803) All matter is composed of extremely small particles called atoms. All atoms of a given element are identical in size, mass, and other properties. Atoms of different elements differ in size, mass, and other properties. Atoms cannot be subdivided, created, or destroyed. read more