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350
Aristotle
Aristotle was the philsopher who opposed Democritus's idea of a smallest unit of matter; the atom. His own belief was that everything was made of the four elements; fire, air, earth, and water. This belief was widely accepted based on his popularity- which was due to the fact he was the tutor of Alexander the Great. -
400
Democritus
After creating the word "atom" and explaining it made up all of Earth;s substances, Democritus created the first atomic model. His model was just simple a round ball. But he did know that atoms are solid, insdestructable, and unique. -
Antoine Lavoisier
THis man put the first elements table together and discovered many of the elments that exist today. Aristotles idea of the main four elements was the basis of most his experiments. Some of those elemts he discovered were hydrogen, oxygen, and sulfur. -
John Dalton
Based off the findings of Democritius, John Dalton created the Atomic Theory of Matter. His theory clearly stated that all matter is made of atoms, that atoms cannot be created nor destroyed and also, atoms of different elements combine in whole ratios to form chemical compunds. This very theory led to many advances in the atomic model. -
Henri Becquerel
Henri Becquerel was related to two very honorable scientists- his father Alexander Edmond Becquerel and his grandfather Antoine Cesar- who led him to study radiation. His discoveries in this field allowed other scientists to further perfect the atomic model. He was even awarded half of the Nobel Prize for Physics in 1903- while the other half was given to Pierre and Marie Curie for their study that branched off of his work. -
J.J. Thomson
J.J. Thomson created the "plum pudding" model. He was able to create this model because he discovered the electron. This model illustrated how he thought that the atom was mostly positive, and negative electrons wandered around the atom. This inspired other scientists to improve on the model. -
Marie and Pierre Curie
This couple made many discoveries in the field of radioactivity. Marie was the one to orignally to begin studying this after Henri Becquerel did. They discovered radium and polonium and later won a Noble Peace Prize. -
Max Planck
This man created the Quantum Theory. This theory stated that energy was given off in little packets of energy. When talking of light, photons were little packages of energy. This helped later with advances in the atomic model because it created energy levels. -
Robert Millikan
Since J.J. Thomson predicted that the electron was 1000 time smaller than the atom, Millikan wanted to prove this hypothesis. After performing an "oil-drop experiment", he proved Thomson right. Before inspiring many other scientists after him, Millikan worked on the Quantum Theory because of Max Planck. -
Ernest Rutherford
After being taught by J.J. Thomson, Rutherford thought that he could improve his teacher's incorrect model. So he came to conclude that the atom had a nucleus, but around that it was mostly empty space. His discoveries inspired students of his to improve on the atomic model. -
Niels Bohr
By attempting to improve Ernest Rutherford's- his former teacher- atomic model, this scientist completely changed the orbit of the electron. By changing this, he also created energy levels within atoms. Bohr even created quantum mechanics, though they orignated from Max Planck's ideas. His model is still used. -
Henry Mosely
By working with Niels Bohr, this man helped develop the atomic numbers. Using x-rays, he found the freguencies of the elements and before his discoveries the numbers were randomly assigned. By doing all this, he created "Mosesly's Law". -
Erwin Schrodinger
This man worked with the Quantum model of the atom. This man disagreed with Bohr's theory, so he created his own that stated that the only way to find the location and energy of an electron in an atom was to calculate its probability of being a certain distance from the nucleus. This influenced the atomic model further. -
Werner Heisenberg
Werner wasn't certain of the Quantum Model, so he challenged it a principle that stated that you can't know the exact velocity and momentum of the electron at the same time, which means you can't know the exact location of the electron. -
James Chadwick
Previously to James Chadwick's studies, Ernest Rutherford had concluded that an atom's nucleus is made of positive matter.This led for Chadwick to question why there was a difference between the atom's neutrons and atomic mass. That very question was the basis of his discovery of the neutron.
