The Fascinating Story of the Periodic Table: The Full Story
5. Dalton's Atomic Theory


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Along with the concept of an element, another thought that existed from ancient times was regarding the nature of matter. The main debate was about whether matter is continuous or discontinuous. Greek philosophers like Lucippus and Democritus, and Indian philosopher Kanad, believed that matter is discontinuous, whereas Aristotle believed that it is continuous.

The debate about nature of matter and the concept of atom was revived by John Dalton, in the first decade of the 19th century with his profound ‘Atomic Theory’. According to him, elements are made up of extremely small indivisible particles called ‘atoms’.



All atoms of an element are identical with respect to mass, size and properties. If you read this sentence carefully, you will realise that Dalton was the first person to propose the atomic weight to be the signature of an element. He was the first person who attempted determination of relative atomic weights and chose hydrogen as the reference element.

Along with explaining the laws of conservation of mass and of constant proportion, Dalton’s theory predicted the law of multiple proportions. This law is proof of the existence of Atoms.

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