It is not at all obvious that atoms exist and there's no reason why there should be an indivisible unit of matter.
Is there an experiment that was conducted which gave strong evidence for the existence of atoms?
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asked Aug 22, 2018 at 1:14
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$\begingroup$ One wonders whether a 141 rep has disqualified you as a "new user be nice" . But I think you should avoid "it is not at all obvious" or at least change to "prior to XXX time in history, it was not obvious," although chemists were certainly cottoning to the idea of elements prior to proof of atoms. $\endgroup$– Carl WitthoftCommented Aug 22, 2018 at 12:37
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$\begingroup$ Did you read en.wikipedia.org/wiki/Atomic_theory#History or en.wikipedia.org/wiki/Atom#History_of_atomic_theory ? $\endgroup$– user5402Commented Aug 26, 2018 at 13:14
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1 Answer
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Consult the Wikipedia page for atom. In its historical introduction, it presents a ladder of theories and discoveries establishing our current knowledge:
- First evidence-based theory
- Brownian motion
- Discovery of the electron
- Discovery of the nucleus
- etc.
French physicist Jean Perrin used Einstein's work to experimentally determine the mass and dimensions of atoms, thereby conclusively verifying Dalton's atomic theory.
https://en.wikipedia.org/wiki/Atom#Brownian_motion
in his studies of the Brownian motion of minute particles suspended in liquids, [Jean Perrin] verified Albert Einstein’s explanation of this phenomenon and thereby confirmed the atomic nature of matter (sedimentation equilibrium).
The discovery of the nucleus by the Geiger-Marsden experiment was another very important step.
In 1909, Hans Geiger and Ernest Marsden, under the direction of Ernest Rutherford, bombarded a metal foil with alpha particles to observe how they scattered. They expected all the alpha particles to pass straight through with little deflection, because Thomson's model said that the charges in the atom are so diffuse that their electric fields could not affect the alpha particles much. However, Geiger and Marsden spotted alpha particles being deflected by angles greater than 90°, which was supposed to be impossible according to Thomson's model. To explain this, Rutherford proposed that the positive charge of the atom is concentrated in a tiny nucleus at the center of the atom.
answered Aug 22, 2018 at 7:17
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2$\begingroup$ “Atom” is indeed the wiki page OP could (should) have consulted. As it says, historically the experiments first regarded as confirming existence of (what we now call) atoms were Perrin’s, on Brownian motion. $\endgroup$ Commented Aug 22, 2018 at 8:30
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$\begingroup$ Thank you. I didn't know and it escaped my attention. I updated the post. $\endgroup$ Commented Aug 22, 2018 at 8:36