Atomic Structure The discovery of atoms began with Democritus, a Greek philosopher, who was the first person to suggest that atoms exist. However Democritus made the false claim that atoms were indestructible which was proven wrong with the development of the atomic bomb (nuclear power), additionally he did not support his idea with scientific evidence or explain the chemical behavior of the atom. Following Democritus was Dalton who took the idea of the atom and explained it and supported it with scientific methods. Atom= The smallest particle of an element that retains its identity within chemical reactions due to maintaining chemical and physical properties. Dalton?s Atomic Theory: All elements are composed of indivisible particles called atoms (later disproved)