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Antoine Lavoisier
Antoine Lavoisier
Antoine Lavoisier was an early chemist and was one of the first to create a comprehensive list of elements. He deduced the Law of Conservation of Matter/Mass sometime in the late 1700's. This allowed for future scientists to conduct research knwoing that the amount of matter they were using would remain constant, and therefore not influence results. -
Period: to
Modern Era
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John Dalton
John Dalton
Dalton was the first modern scientist to make advances in the field of atomic theory. In fact, he invented the Atomic theory, creating 5 main points that are still held valid today. He assumed the atom was solid, like a marble, and thus published his idea. -
Henri Becquerel
Henri Becquerel discovered the concept of natural radiation. Designing an experiment with the Curies, he realized that some substances emit a form of radiation. As this did not directly effect any knowledge of atoms at the time the concept of the atom did not change. -
J.J Thompson
J.J Thompson
J.J Thompson realized that were several components that made up the atom. He discovered electrons, and decided they were spotted throughout the ball shape of the atom introduced by Dalton creating the "plum pudding" model. Also he determined that atoms could have isotopes. He taught Rutherford, who later improved his model, -
Pierre and Marie Curie
Marie Curie and her husband Pierre discovered the concept of radioactivity. From this later scientists were able to use radiaton to bombard the atom and determine its other components. They worked with Becquerel to discover his natural radiation . This discovery did not directly influence the model of the atom. -
Max Planck
Max Planck
Max Planck is known as the father of quantum mechanics. This allowed later scientists to disocver other parts of the atom, and presented the problem of electron placement, later adressed by Bohr. He helped Einstiend develop his photoelectric effect which helped determine neutrons. -
Robert Millikan
Millikan's Atom Model
Robert Millikan is most notable for his discovery of the actual charge of the electron. J.J Thompson had already discovered the charge-to-mass ratio so the calculation of the charge directly resulted in the calculation of the mass of the electron. This allowed them to better understand the charges taking place within the atom. -
Ernest Rutherford
Ernest Rutherford
Ernest Rutherford, through his famous gold-foil experiment, deduced that the atom was composed of a dense nucelus surrounded by electrons; this as opposed to Thompson's "plum pudding" model. He also discovered the proton,the postively charged particle in the nucleus. He was a student of Thompsons and taught Bohr and Chadwick, who later improved his model. -
Niels Bohr
[' >Niels Bohr](<a href='http://1.bp.blogspot.com/_IoU3bEFUwWc/SCw4-MCaf9I/AAAAAAAAB8s/BPNcuBcZ9j4/s400/Niels+Bohr.jpg)
Niels Bohr introduced his model in 1913. He theorized that electrons had a quantifiable energy and consisted of several energy levels. This supplemented Rutherford's model of a dense nucleus; however, instead of a single cloud of electrons, he proposed a series of orbits around the nucleus. He was a student of J.J Thompson and also collaborated with Rutherford. -
Henry Mosely
Henry Mosely
Henry Mosely was the first to provide evidence to Bohr's theory of the relation between protons and the atomic number of an atom. This allows chemists to easily organize elements by their proton count and seperate them by property with a specific characteristic. He was influenced by Rutherfords work, and eventually supported the Bohr Model with his discovery. -
Erwin Schrodinger
Erwin Schrodinger
Erwin Schrodinger created an equation to determine how the quantum state of a physical stystem (most commonly applied to the atom) changes over time. His papers, published in 1926, were a derivative of the heisenbergy principle and Bohr's earlier model. He contrtibuted to themost modern model used today. -
Werner Heisenberg
Werner Heisenburg
Heisenburg is famous for his contributions in the field of quantum mechanics, most notably his uncertainty principle. His principle states that it is impossible to know both the position and momentum of a particle. Therby declaring Bohr, his mentor's, model incorrect in its given orbits and levels -
James Chadwick
James Chadwick
In 1932 Chadwick discovered the neutron. This enhanced the model proposed by Rutherford, his teacher, by by introducing a new particle that held together the protons in the nucleus. -
Period: to
Ancient
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Democritus
Democritus
Democritus (460-370 BC) First proposed the idea of an indivisible substance that makes up all matter. He called this indivisible substance "atomos". He had no way to test or see the atom so he assumed it was a miniscule sphere of sorts. He proposed his idea in early 3rd century BC but was later rejected by Aristotle. -
Aristotle
Aristotle
Aristotle (384-322 BC) rejected Democritus' idea of an indivisible substance. He believed that everything was made up of the 4 elements, fire, water, air, earth. His idea he proposed in late 3rd century BC and held sway for nearly 2000 years.
