Atoms – Historical Development
		• To some Greeks, were smallest “indivisible” unit of matter • In 1700’s, 1800’s discovery of chemical “elements” (H, He, C, O, N, ...) somehow made of different kinds of atoms • In early 1900’s, parts of atoms and reasons the elements differ understood • In early to mid 1900’s ways to change one kind of atom into another understood – radioactive decay – fission – fusion