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460
Democritus
Born in Abdera, Greece (460-370 BC). His theory stated that "the universe is composed of two elements: the atoms and the void in which they exist and move". Democritus hypothesized that atoms cannot be destroyed, differ in size, shape and temperature, are always moving, and are invisible. He believed that there are an infinite number of atoms. -
Antoine Lavoisier
Antoine Lavoisier was basically discovered substances such as oxygen and hydrogen. He also was the the one who came up with the Law of Conservation of Mass from his experiment. He was not the one who thought about atoms but he did think about the different elements and that lay out some great groundwork material. -
John Dalton
English teacher and public lecturer. He stated that all elements consisted of tiny particles called atoms. He was also the one who discovered that all atoms of the same element have same masses wheras atoms of different elements have different masses. He also said that atoms could not be divided into smaller particles and they could not be destroyed. -
Henri Becquerel
French scientist who discovered that uranium compounds darken photographic plates. He is also known for discovering radioactivity during his uranium experiment. -
Marie and Pierre Curie
Both did extra research on radioactivity and contributed a lot of information in that field. This research led them to discover two new elements, radium and polonium. -
J. J. Thompson
He discovered a way to seperate atoms and molecules from positive rays. He also found out that an atom can be divided and he was also one of the firsts to realize that atoms were made of both postive and negativly charged particles. He proposed the Plum Pudding Model before the discovery of the nucleus. Therefore he helped a lot in the understanding of atom structure. -
Max Planck
German theoretical physicist. He discovered a formula that found the amount of energy that is given of when the energy levels of electrons are changed. He found out that electromagnetic energy is released in quantized amounts. -
Ernest Rutherford
Found the positive charged area of an atom and called it the nucleus. He discovered the nucleus through an experiment that he performed called the golden foil experiment. In this exp. he shot alpha rays through goil foil and he noticed that the rays did not pass through and some particles deflected. -
Robert Millikan
American experimental psysicist. Millikan was the one who discovered that the overall charge of an atom is neutral. Did the oil-drop experiment and found out that the wieght/mass of an electron was very very small. -
Henry Moseley
British Physicist. Sorted the elements of the periodic table in the order of thier atomic numbers. He contributed a lot to the study of physics since he did some research before he passed away. -
Niels Bohr
Student of Ernest Rutherford. The one who created the Bohr model of an atom. Bohr was the first to discover that electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element. -
Werner Heisenberg
German Physicist. He discovered that the position and momentum of a particle are related. The more precise the postion of a particle, the less precisely the momentum is known. This is called the uncertainty principle. -
Erwin Schrodinger
Austrian psysicist. Took the Bohr Model one step further and created the quantum mechanical model. This model makes it easier to predict the location of the electron. In short, this model introduced the concept of "sub-energy". -
James Chadwick
Discoverer of the subatomic particle, neutron. He said that they had no charge and they were there to stabilize the nucleus. -
Aristotle
(384-322 BC) Great philosopher of Greece. Originally did not believe in the atomic theory. He believed that all materials on earth were made from Earth, Fire, Water or Air. His theory was proven wrong 2,000 years later!
