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450 BCE
Democritus-The history of the atom really begins with Democritus.
Democritus wondered what would happen if he cut an object(Apple) into smaller and smaller pieces. He thought that once you get to a certain point the pieces wouldn't be cuttable any more, and so he called these pieces "uncuttable" pieces atomos, which would be later remained to the modern term atom. Democritus had only theorised about the atom but never drew on more than that because he didn't experiment on it. Democritus contributed the idea of atoms. -
John Dalton was a renown English chemist, physicist, and meteorologist
John Dalton was the first to really pick up on the idea of atoms and his atomic weight theory. John Dalton in 1803, came up with the first atomic weights chart. http://tinyurl.com/22l6k99 -
John Dalton
In 1808, Wanting to expand on his atomic weight theory, Dalton introduced his belief that atoms of different elements could be universally distinguished based on their varying atomic weights. -
JJ Thomson Thomson was a Nobel Prize winning physicist whose research led to the discovery of electrons. Thomson's ionized neon experiment which he streamed ionized neon into a magnetic field and electric field, with this he discovered isotopes.
Thomson's discovery of the electrons is his biggest contribution to the atom and science, which happened in 1894 from his researching of cathode rays. Thomson originally called these particles, "corpuscles," though now they are known as electrons. In 1912 Thomson made famous discoveries from his experiment with channeling ionized neon through a magnetic and electric field which led him to discover that neon is composed of two different kind of atoms, and proved existence of isotopes. -
Ernest Rutherford-Ernest Rutherford is the father of nuclear chemistry and nuclear physics. Rutherford contributed the discovery of the atomic nucleus, the alpha and beta particle.
Rutherford's greatest contribution to the atom was the discovery of the atomic nucleus, which was in 1909. Rutherford discovered the atomic nucleus form his gold foil experiment, where he shot an alpha particle through a sheet of gold, some went straight through, but some were deflected enormously, even some, "bouncing" straight back from the gold. So Rutherford discoverers the nucleus from him knowing that most was empty space, but in the middle it's very dense. -
Niels Bohr- He discovered the nucleus orbiting the nucleus, nuclear fission(formed the first nuke) and quantum physics.
Niels Bohr contributed quantum physics, which is arguably his biggest contribution, In 1912, he also experimentally had established that the atom consists of a heavy positively charged nucleus with substantially lighter negativlely charged electrons circling around it at a considerable distance. This was the Bohr model introduced by Bohr in 1913 showing that in the nucleus it is highly positive(protons) and there are negatively charged particles(electrons) orbiting the nucleus.
