Atomic Pioneers - John Dalton
“Matter, though divisible in an extreme degree, is nevertheless not infinitely divisible…I have chosen the word ‘atom’ to signify these ultimate particles.” — John Dalton
John Dalton (1766-1844) was a man of innovative intellect and many interests who was born in Cumberland, England. By his mid-teens, he was the teacher at the Quaker school he had attended. He later taught college-level mathematics and chemistry. At 27, he wrote a book on meteorology and kept daily weather observations for 46 years. Dalton did the first real study of colorblindness, a condition he shared with his brother and which is still often called “daltonism.” He measured the height of local mountains using a barometer and did experiments with vapor pressure in relation to temperature.
Yet Dalton’s work with atomic theory is considered his most important. Contemporaries, including Thomas Thomson and William and Bryan Higgins, probably influenced him. His work, however, contained key ideas that theirs had not, including a method of calculating relative atomic weights. His main points were:
1. Elements are made of extremely small particles called atoms.
2. Atoms of a given element are identical and differ from those of other elements.
3. Atoms cannot be subdivided, created, or destroyed.
4. Atoms of different elements combine in simple whole-number ratios.
5. In chemical reactions, atoms are combined, separated, or rearranged.
Dalton was the first to establish a table of atomic weights.
Dalton was one of very few scientists to be honored with a sculpture while still living. A unit of measure — the dalton (symbol da) bears his name. It is 1/12 the mass of a neutral atom of Carbon 12. #ManhattanProjectNPS #FindYourPark #EncuentraTuParque
Image caption: Scientist John Dalton, 1766-1844, by Charles Turner
Image credit: Public domain, drawing by Charles Turner
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