Democritus and Epicurus proposed the existence of indivisible particles (atoms) in ancient Greece.
John Dalton
John Dalton developed the atomic theory in 1803, stating that atoms are indivisible, indestructible, and indivisible, and that atoms of the same element are identical.
J. Thomson
J. Thomson discovered electrons in 1897 using his cathode ray tube experiment, revealing negatively charged particles.
Ernest Rutherford
Ernest Rutherford discovered the atomic nucleus in 1911 through his gold foil experiment, demonstrating that protons and neutrons form the nucleus.
Niels Bohr
Niels Bohr developed the concept of energy levels and quantization in 1913, introducing the idea that electrons orbit around the nucleus in energy levels.
