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460 BCE
Democritus
He came up with the atomic theory that stated that the world is made up of small, hard, and invisible particles. -
John Dalton
Dalton proposed that all matter was composed of atoms, and that they were indestructible building blocks in our world. He also discovered that atoms can be different sizes and masses. -
Dmitri Mendeleev
He created a table that organized elements based on their atomic weight. -
Eugene Goldstein
Goldstein discovered protons due to his experiment with using cathode rays which knock electrons off of atoms. He also discovered properties of the cathode rays which helped in later discoveries of the electron. -
J.J Thomson
He discovered the electron by experimenting with cathode ray tubes. This expressed how cathode rays are negatively charged. He also experimented with positive particles with neon gas. -
Max Planck
Planck discovered that energy is given off by a black body called quanta. He described this idea through Planck’s law. -
Robert Millikan
He discovered the value of e for an electron charge. He discovered this through his oil drop experiment. -
Ernest Rutherford
He overturned the model that Thomson created, and instead demonstrated how the atom has a tiny but heavy nucleus. He also invented a way to use alpha particles emitted by a radioactive element to understand the small world of atomic structures. -
Niels Bohr
Bohr created the Bohr model of the atom. With this model he suggested that energy levels of electrons are discrete and that they revolve in a study orbit around the atomic nucleus but can move from one energy level to another. -
Erwin Schrodinger
He created a more extensive model to the Bohr model of the atom by using a mathematical method to understand and predict the likelihood of an electron being in a certain position on the atom. This model is known as the quantum mechanical model of the atom. -
James Chadwick
Chadwick contributed to the science community by discovering what was in the center of the atom, neutrons. -
Werner Heisenberg
He is best known for his uncertainty principle and theory of quantum mechanics. He won a Nobel Peace Prize for Physics for his research in that area.
