You cut it successively into ever smaller pieces. The idea of atoms was not seriously revived until the early years of the nineteenth century when John Dalton, an English schoolteacher, proposed his atomic theory to explain why it is that pure materials always have a fixed composition. He proposed not only that atoms were the ultimate particles of matter, but also that there are many different kinds of atoms. These atoms are the building blocks of all matter, and the individual kinds of atoms are the chemical elements. Other substances are compounds and contain more than one element.
Gold is an element, but water is a compound, being composed of both hydrogen and oxygen atoms.
The major change in our thinking since Dalton's time has been the realization that atoms are not the ultimate particles of matter. The different kinds of atoms differ in the relative numbers of these subatomic components. About ninety different elements are found in nature. A relatively small number of manmade elements have been produced by taking advantage of knowledge of the fields of nuclear physics and nuclear chemistry. Interestingly, the concept of radio-activity refutes one of the original tenets of Dalton's theory, that atoms can never be created or destroyed.