Atomic theory

The Atomic Theory posits that matter is composed of discrete units called atoms, which combine in simple whole-number ratios to form chemical compounds. It laid the groundwork for modern chemistry and provided a systematic explanation for chemical reactions based on the combination and rearrangement of atoms.
 John Dalton England 1803 Atomic theory

The Atomic Theory posits that matter is composed of discrete units called atoms, which combine in simple whole-number ratios to form chemical compounds. It laid the groundwork for modern chemistry and provided a systematic explanation for chemical reactions based on the combination and rearrangement of atoms.