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Aristotle
Aristotle was a Greek philosopher. He believed the existence of four elements: water, fire, earth, and air. His influences were Nichomach (father) and Plato, his teacher. Aristotle thought the atomic theory had no merit and thought the idea was worthless. Hence, there was no point in studying it. -
440
Leucippus and Democritus
Coming from Leucippus and Democritus, no work was completed. Theories were developed. He believed that all elements are made up of various indivisible elements called atoms. This in greek means the one the you cannot "cut" any further. Although, he did ask himself could an atom be split. There was no experiment conducted. -
John Dalton
Dalton's observations helped him to discover the partial pressures of gases. Dalton did more experiments to prove this and soon found that he could use this to find out the atomic weight of each atom. He found that atoms differentiate between specific elements and weight. His work was influenced by the earlier work of Democritous. -
William Thomson
The first attempt to construct a physical model of an atom was made by William Thomson (later elevated to Lord Kelvin) in 1867.Kelvin, in 1903, proposed that the atom have the newly discovered electrons embedded somehow in a sphere of uniform positive charge, this sphere being the full size of the atom. He was influenced by J.J also. -
J.J Thomson
The British physicist Joseph John Thomson found that in an ample amound of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube. In 1904 Thomson suggested a model of the atom as a sphere of positive matter in which electrons are positioned by the forces of the electrons. His last important experiments focused on determining the nature of positively charged particles. -
Ernest Rutherford
Ernest Rutherford published his atomic theory describing the atom as having a central positive nucleus surrounded by negative orbiting electrons. This model suggested that most of the mass of the atom was contained in the small nucleus, and that the rest of the atom was mostly empty space. Rutherford came to this conclusion following his famous gold foil experiment. This experiment involved the firing of radioactive particles through minutely thin metal foils. He was influence by J.J Thomson. -
Robert Millikan
Millikan measured the charge on an electron with his oil-drop apparatus. An "atomizer" from a perfume bottle sprayed oil or water droplets into the sample chamber. Some of the droplets fell through the pinhole into an area between two plates. Particles that did not capture any electrons fell to the bottom plate. His work was also influenced by J.J. He proved Thomson's hypothesis that the mass of an electron is at least 1000 times smaller than the smallest atom.
due to gravity. -
Niels Bohr
Influenced by Ruthford, Bohr applied the quantum theory to his atomic structure by thinking electrons orbit around the nucleus. He also found that there might be possible energy levels in which these electrons are located. -
Werner Heisenberg
Heisenberg worked out that particles had a lot more energy over short distances than expected. He realized that a particle can borrow energy.The relationship he came up with was the position and energy of a particle can only be known to a certain amount. This is believed to be the way a particle escapes the charge at the nucleus of an atom and is radioactive decay occurs. Bohr was Heisenberg's influence. -
Erwin Schrodinger
Erwin Schrodinger took the ideas developed by de Broglie, Heisenberg and others and put them together in a single equation that is named after him. Solving this equation can in principle predict the properties and reactivities of all atoms and molecules. He foudn that the orbitals, associated with each energy, determine where the electrons are located. Louis de Broglie influenced the word of Schrodinger. -
Paul Dirac
He was an English mathematician and theoretical physicist. His first major contribution was a general form of quantum mechanics. Dirac developed ideas of Enrico Fermi, which led to the Fermi-Dirac statistics. He then applied Albert Einstein's special theory of relativity to the quantum mechanics of the electron and showed that the electron must have spin of 1/2. He was influenced by his own father. -
James Chadwick
James Chadwick proved that the atomic nucleus contained a neutral particle which had been thought of before by Ernest Rutherford. Previous findings became clearer to him(the negative charge of the electron and the positive charge of the proton canceled out), it was beginning to grow clear how chemical bonds form within the electron shells of the atom, and it was suddenly clear why different atoms absorbed and emitted only very specific colors of light.
