John Dalton

John Dalton (6 September 1766–27 July 1844) was a British chemist and physicist. He was born in Cumberland to a Quaker family. He is best known for his discoveries in atomic theory. He also made the first important studies of color blindness.

Dalton collecting marsh gas by Ford Madox Brown about 1890. Mural in Manchester Town Hall

John Dalton

Dalton's atomic theory

Dalton's Atomic theory is a scientific theory about atoms. Dalton made the theory to explain why the elements would combine in certain ways^[1] The idea of atoms was already known at the time, but not widely accepted. Dalton's theory of atoms was based on actual observation. Ideas about atoms were based on philosophy before John Dalton came up with his theory.

His theory stated that:

• Atoms cannot be divided^[2]
• Everything is made of atoms^[2]
• Atoms can not be made or destroyed, just as energy
• Atoms are tiny particles^[2]
• Atoms can only be joined in special ratios
• Atoms of the same element are the same, because they have the same atomic mass^[2]
• Chemical reactions are made when atoms are moved around, put with other atoms or taken away from a group of other atoms

Further readings

• Claus Bernet: John Dalton (1766-1844), in: Biographisches-bibliographisches Kirchenlexikon, 31, 2010, 309-332.