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500 BCE
Democritus
He was the first to suggest the existence of the atom. He created the first atomic model. That contribution helped other scientists with their discoveries. He had stated, "everything is composed of “atoms”, which are physically, but not geometrically, indivisible. Between atoms, there lies empty space. Atoms are indestructible." His theory was sometimes questioned since he could not explain the chemical side of the atom. -
Antoine Lavoisier
He discovered the part oxygen is in combustion. (Using enough oxygen for fuel to make CO2 and H2O.) He named Hydrogen and Oxygen. He also helped with the construction of the metric system, and wrote the first list of elements. He predicted the existence of many elements including silicon and sulfur. -
John Dalton
He developed the modern atomic theory, based of of Democritus's. He also researched colorblindness. The last part of his atomic theory was that when atoms from different elements are combined, rearranged, or separated, chemical reactions will take place. HIs theory also included compounds (combination of different elements). -
Dmitri Mendeleev
Dmitri Mendeleev was the first one to notice recurring patterns in elements by using his knowledge of the elements and their physical properties. He then arranged them by their atomic weight and was able to predict new elements -
Eugene Goldstein
Eugene Goldstein was a German physicist that discovered the idea of protons. He discovered them using canal rays. Canal rays are beams of positive charged protons. He was then credited with the creation of protons -
J.J Thomson
He invented the Cathode Ray. High energy was transferred from the negative side of the cathode to the positive side through a vacuum sealed container. It produced a ray of electrons, which is what he discovered. He created the plum pudding model of the atom. He also discovered isotopes from sending ionized neon across a magnetic/electric field of energy. -
Robert Millikan
He used a falling-drop method. That balanced a downward gravitational pull with an electrical force going upwards. Between two electrodes, he figured out that an electron's charge was negative. It would help other scientists with ways to find the mass of other particles. -
Ernest Rutherford
In 1911 Rutherford and some coworkers tested the current atomic structure theory, they found that this current theory was wrong. He then proposed that he atom is mostly filled with empty s[ace, and concluded with the discovery of the nucleus -
Niels Bohr
He was the one who came to the conclusion that atoms have a nucleus that is charged, with electrons surrounding it. It would eventually turn out to be a more accurate representation of the atom. -
Henry Moseley
Henry Moseley was a british physicist that discovered the series of atomic numbers, this linked the atomic number of the element to their electron structure. Also, he discovered that the wavelength of x-rays became shorter as the atomic weight increased -
Henry Moseley
He developed the Moseley Law, which is an empirical law that related to x-rays that are emitted by atoms. He studied physics -
Erwin Schrödinger
Erwin Schrödinger was an Austrian physicist that changed the theory of wave mechanics, to the Schrödinger wave equation. He tracked the movements of electrons in terms of wave mechanics -
James Chadwick
James Chadwick discovered neutrons, and how they had no charge. That changed the appearance of the atom, and allowed the production of atomic bombs. -
Werner Heisenberg
Werner Heisenberg was the first one to discover the idea of atoms having electron patterns. He helped clarify the view of an atom because now we can compare the atoms by their movements and electrons
