John Dalton: The Birth of Atomic Theory

John Dalton (1766–1844) was an English scientist who laid the foundation for modern atomic theory.
He proposed that all matter is made of tiny, indivisible particles called atoms.
Dalton believed atoms of the same element are identical, while atoms of different elements differ.
He explained how atoms combine in fixed ratios to form compounds.
His theory helped make sense of chemical reactions as rearrangements of atoms.
Dalton introduced the idea of using symbols to represent different atoms in diagrams.
He studied gases and discovered that each gas exerts pressure independently in a mixture—known as Dalton’s Law of Partial Pressures.
Dalton was also a pioneer in studying color blindness, sometimes called “Daltonism.”
While some details of his theory were later revised, his core ideas remain central to chemistry.
Dalton’s atomic vision turned chemistry into a true science of matter’s building blocks.