The basic building block of Chemistry is the atom it is therefore useful to define what an atom actually is.
Atoms are made up of positive (protons), negative (electrons) and neutral (neutrons) subatomic particles. Physics further breaks these particles down into fundamental particles that are not discussed here. Instead, we start here with our study of chemistry – the discovery and the modern definition of the atom.
Democritus – 450 B.C. – coined the name atomos meaning “uncuttable” and defined it as the term for “the smallest indivisible particle of matter.”