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Democritus - The Atomic Theory(460 B.C.)
460 B.C. - Democritus talks about the atom as the smallest particle of matter. He defines the atom as an indivisible particle that cannot be broken down any further. This explains natural occurrences such as the existence of elements. He formulated the atomic theory. (Date put at 1700 to make timeline smaller) -
Antoine Lavoisier - Law of Conservation of Mass
Antoine Lavoisier was a French chemist. He is widely considered to be the "Father of Modern Chemistry." He is known for the law of conservation of mass, which states that mass is neither created or destroyed in chemical reactions, meaning that at the beginning and end of a reaction the mass of any element stays the same. This also means that atoms can neither be destroyed or created by a chemical reactions. -
Joseph Proust - Law of Definite Proportions
Joseph Proust was a French chemist. He is well known for his law of definite proportions, which states that a chemical compound always contains exactly the same proportion of elements by mass. -
John Dalton - Solid Sphere Model
John Dalton was an English chemist, meteorologist and physicist. He is wellknown for his early work in the development of the modern atomic theory. He created the solid sphere model, in which atoms are seen as solid, indestructible spheres (like billiard balls). The model explains a lot of chemical properties, explains chemical change, and confirms the basic laws of chemistry. -
J.J. Thomson - Plum Pudding Model
J.J. Thomson was a British physicist. Thomson discovered the electron through his cathode ray tube experiment. He also created the plum pudding model, before the discovery of the atomic nucleus in, 1904 in order to add the electron to the atomic model. -
Ernest Rutherford - Gold Foil Experiment
Ernest Rutherford was a New Zealand physicist. He became known as the "father of nuclear physics." He is well known for his gold foil experiment. The gold foil experiment was performed to prove the structure of the atom in 1909. The results were unexpected and resulted in the discovery of the nucleus and the proton, both named by Rutherford. -
Albert Einstein - Quantum Theory
Albert Einstein was a German physicist. He helped develop the quantom theory along with Schrödinger. He is also known for his general theory of relativity and creation of the atomic bomb. -
Neils Bohr - Bohr Model
Neils Bohr was a Danish physicist. He made many contributions to the understanding atomic structure and quantum theory. Bohr developed the Bohr model, in which he proposed that electrons had discrete energy levels, and that the electrons orbit around the nucleus, and are able to jump from one energy level to another. There is a maximum number of electrons allowed in each energy level. -
Erwin Schrödinger - Quantum Theory
Erwin Schrödinger was an Austrian physicist who helped work on the quantum theory and the quantum mechanical model. -
James Chadwick - Discovery of the Neutron
James Chadwick was an English physicist who discovered the neutron in 1932. He studied under Ernest Rutherford. -
Werner Heisenberg - Uncertainty Principle
Werner Heisenberg was a German physicist and one of the main creators of quantum mechanics. His work was published in 1925. In 1927, he formulated the uncertainty principle: "the uncertainty principle is any of a variety of mathematical inequalities asserting a fundamental limit to the precision with which certain pairs of physical properties of a particle known as complementary variables, such as position x and momentum p, can be known simultaneously." -
Julius Oppenheimer
Julius Oppenheimer was an American physicist. He is included in the people who are called "father of the atomic bomb" for his role in the Manhattan Project. He also helped with quantum mechanics and the quantum theory.