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460 BCE
Democritus
Democritus was born in Greece. He was a major figure in the early development of the atomic theory. He believed that everything in the universe was made of "atomos", which were tiny, unseen particles. Democritus proposed that said particles were non-porous and indestructible. He also said that atoms were all the same, and that different materials were just made up of the atoms with different textures and shapes, and he said different colors were made with different atoms, too. He died in 370 BC. -
John Dalton
John Dalton was born in Eaglesfield, England. He originally took interest in studying meteorology and colorblindness. Dalton started to study liquids and gases, and experimented with both. He wondered what made up the gases he studied, so he looked into atomic theory. He combined different elements to form new compounds, and later determined that atoms were, in fact, existent. He went further than Democritus by stating different elements' atoms had different masses. He died on July 7, 1844. -
J.J. Thomson
JJ Thomson was born in Cheetham Hill, England. In his 40's, he began studying Cathode Rays, which was a popular subject to study among physicists at the time. Through his experiments, he made two groundbreaking conclusions. His first finding was that atoms were made up of much smaller particles (which he dubbed "corpuscules", later named electrons). Second, he discovered the existence of isotopes while using the Mass Spectrometry technique. He died on August 30, 1940. -
Ernest Rutherford
Ernest Rutherford was born in Nelson, New Zealand. One of Rutherford's major breakthroughs was the discovery of the nucleus. He figured this out by conducting an experiment with rays and gold foil, and realized that the center of particles had a positive charge. He proposed that atoms had a positively charged center and the electrons surround the nucleus randomly, and there was a lot of empty space. He also developed the Rutherford model which was a big step forward. He died on October 19, 1937. -
Niels Bohr
Niels Bohr was born in Copenhagen, Denmark. Bohr's major discovery, and arguably one of the most important advancements in Atomic Theory as a whole, was his model of the atom, dubbed "The Bohr Model". Bohr was around just when the nucleus was discovered by Rutherford, and when Rutherford proposed his atomic model. Bohr theorized that electrons existed in orbitals around the nucleus, rather than randomly floating around. He died on November 18, 1962. -
Erwin Schrödinger
Erwin Schrödinger was born in Vienna, Austria. His major contribution to Atomic Theory focused on electrons. He used mathematical equations to determine the positions and wave properties of electrons. He lived during the same time as Niels Bohr, and piggybacked off of Bohr's findings. He died on January 4, 1961.
