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?


1 Answer 1


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.


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.


  • 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. $\endgroup$ Aug 22, 2018 at 8:30
  • $\begingroup$ Thank you. I didn't know and it escaped my attention. I updated the post. $\endgroup$ Aug 22, 2018 at 8:36

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