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350
Airstotle
He was responsible for people not beliving that everything was made up of atoms. Peoople belived this for 2000 years. He belived that there was not a smallest part of matter. He also belived that diffrent substances were made of earth, fire, water and water. There is no atomic model for the fact that he didn't belive in the atom. -
400
Democritus
He was responsible for the idea that everything is made up of matter which were tiny particles. He made this discovery in 400 b.c. This contradicts the idea that Aristotle had, that there wasn't anything small that made everything up. But in later times John Dalton revised the atomic theory. -
Antoine Lavoisier
He formulated the theory for combustion, by looking back at Aristotles ideas. He made imporant discoveries of composition, such as water and air. He also discovered the law of convervation on masses. He disprived that when metal became powered, it only did this because it had taken in oxgen when burning. This all happened around 1780. -
John Dalton
Dalton was primarily responsible for the theory that elements can be distinguished by their weight. He first discovered this in 1803. He also gave the following theory, that all matter is made up of atoms, all atoms of the same element are identical in mass and their properties, compounds are formed or two or more diffrent types of atoms, and a chemical reaction is a rearrangement of the atoms. This will help the devolpment of the atom in later years. -
Henri Becquerel
Becquerel was primarliy responsible for the discovery of radioactive elements. He discovered the elements thorium, polonium and radium. His discovery happened in 1896. Becquerel made the contribution of information on radioacitivity. This added to the knowledge of atoms, and the fact that they can be radioacitive. -
Max Planck
Planck was responsible for the quantum theory. This was published in two books, the first was Thermodynamick (1897), and the second was Theorie der Wärmestrahlung (1906). This discovery lead to the understanding of energy levels in the atom, and because of this the atom model was able to advance. -
J.J. Thomson
J.J. Thomson is primarily responsible for the idea of subatomic particles called elections. He discovered this in 1897. Before this we didnt know the atom was made up of a fundamental unit 1000 times smaller. -
Marie & Pierre Curie
Together they are responsible for the isolation of polonium and radium. They discovered this in 1898. The contrubtion of the field of radioactivity was also done by these two. This adds to Henri Becqyerel's discovery of uranium. For this they shared the Nobal Prize for Physicis in 1903. -
Ernest Rutherford
Rutherford was primarily responsible for the discovery of the proton. He found this out by conducting the gold foil experiment. Not until 1920 wsa the proton named, it was named proton becasue of the positive charge. Rutherford contributed the the idea of the proton. -
Robert Millikan
Millikan made the discovery of the charge of the electron, and that this quanity was the same for every electron. This discovery was made in 1910. This enhances the previous models, because it means that all the electrons in every atom equal the same. -
Niels Bohr
He is primarily responsible for the Bhor model, which is a nucleus in the center and the elections orbiting around it. This contrubtion was made in 1913. He made contributions to the understanding of atomic structre. This enhances the previous models because it shows elections arent in the nucleus, rather they are floating around the nucleus, like planets do around the sun. -
Henry Mosely
By observing and measuring the x-ray spectra he discovered that there was a realtionship between wavelength and atomic number. This is known as the Mosely's Law. Before this discovery was made, atomic numbers were thought of as arbitary numbers, abd were based on weight. This added to how the periotic table was set up. -
Werner Heisenberg
Heisenberg made the discovery of the Uncertainty Principle. This was said that electrons didn't travel in neat orbits, and electrons with a certain amount of photons will change momentum. -
Erwin Schrodinger
Schrodinger was responsible for the quantum mechanical model. This went further than the bohr model, and doesn't define the exact path of the electon. This model also shows the clould, which is where the elections are at, and when the cloud is most dense the electons are easily found. He made this discovery this in 1926. -
James Chadwick
Chadwick was responsible for the discovery of the neutron. He discovered this in 1932. His contribution was that the atom had three parts and that the elections aren't in the nucleus. This added on to the ideas of others because he says that their isn't just protons and electrons, there are also neutrons.
