New System of Chemical Philosophy

John Dalton's New System of Chemical Philosophy (1808–27) was a landmark in the development of atomic theory. Dalton proposed that elements are characterized by the mass of their atoms and that atoms of an element are identical in shape, size, and mass. He also suggested that atoms combine in small, whole-number ratios to form molecules. This theory provided a scientific basis for understanding how elements combine to form compounds and offered a reason to believe in the existence of atoms. Dalton's work built upon experimental observations and laid the groundwork for modern chemistry, though some of his initial assumptions, such as the indivisibility of atoms, were later disproven.123