Apparently, this is how it went.
1.....400 B.C. Democritus’ atomic theory posited that all matter is made up small indestructible units he called atoms.
2...1903 Hantaro Nagaoka proposed an atomic model called the Saturnian Model to describe the structure of an atom.
3....In 1955 Professor of Physics, Erwin Mueller, became the 1st person to see an atom, using a field ion microscope of his own design.
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1938 Lise Meitner, Hahn, Strassman discovered nuclear fission.
1942 Enrico Fermi created the first man-made nuclear reactor.
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Not quite, that's a fairly simplistic view of how it went.
1. First eastern concept of atomism dates back to Indian Jainism in ~6th century BC.
2. First western concept of atomism is 5th Century BC, by Leucippus (Democritus' teacher).
3. Democritus systematises Leucippus' views, and coined the phrase atom. (Well the greek word atomos IIRC)
4. Robert Boyle expands on corpuscularianism in the mid 17th century.
5. Newton then uses corpuscularianism in his theory on light in the 1670's.
6. The chemist Lavoisier defines elements as substances that can't be broken down further in mid/end 18th century.
7. John Dalton uses atomism in the early 19th century, to describe how elements always react in whole number ratios. Leading him to postulate a hypothesis that ultimately leads to atomic theory.
8. At around the same time Robert Brown is looking into Brownian motion.
9. Brownian motion is analysed by Einstein in early 20th century.
10. Einstein's work is then used by Jean Perrin to experimentally verify Daltons hypothesis.
11. Mendeleev publishes his first version of the periodic table of elements.
I think I could describe another 20-30 (still wouldn't be everyone) notable individuals who contributed to atomic theory. But I'll need to get to the rest of my science history/text books which involves getting a step-ladder. My wife's asleep and I'm not sure she'll appreciate the noise of bringing it in through the bedroom door to the garden.
Ta Ta