Know about the first model of the atom.

The ancient Greeks were the first to use the word atom,which means indivisible,to describe the smallest particle of any substance. Its actual existence was not established until yhe nineteenth century when John Dalton, an English chemist,put forward a theory to describe the nature of the atom.The atom is now considered to be the basic unit of simple substances or elements.An atom is the smallest particle of an element which can take part in a chemical reaction or an atom is the smallest part of an element that can ever exist and still possess the chemical properties of that element.