sentence: Atoms are the smallest pieces of matter.
sentences_before: In chemistry and physics, the 'atomic theory' explains how our understanding of the atom has changed over time.
sentences_after: The first idea of the atom came from the Greek philosopher Democritus. A lot of the ideas in the modern theory came from John Dalton, a British chemist and physicist.
concept_name: atom
headings: Atomic theory
categories: Nuclear physics Chemistry