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450 BCE
Elemental Model
The first theories of the atom were proposed by the Greeks. THe Greeks used the elemental model to explain what atoms were made of. The model stated that all atoms were made of fire,water,earth, and wind. -
442 BCE
Democritus
Lived in Ancient Greece from 460-370 BC. One of the founders of the atom. Created a model that stated everything was made of matter called atoms. Stated atoms are indestructible and unchangeable. -
Period: 400 to
Stalemate of Discovery
For around 2000 years there were no further breakthroughs in the discovery of the atom. -
Antoine Lavoisier
Lavoisier lived in France during the 18th century. Lavoisier discovered the Law of Conservation of Mass. This stated The total mass of the products of a chemical reaction is always the same as the total mass of the starting materials consumed in the reaction. To prove this he used multiple burning lenses to create high temperatures and chemical reactions. His works led to him being considered the father of chemistry Unfortunately he lived during the French Revolution and was executed. -
John Dalton
John Dalton lived in the UK from 1766 to 1844. Dalton discovered the idea of atoms of different elements vary in size and mass which was a differentiated view from previous philosophers like Democritus. Dalton experimented with gases to prove his theory. He was actually colorblind and proved it was genetic. Dalton became a professor at the New College in Manchester. -
Billiard Ball Model
Created by John Dalton who used billiard balls as a model to show atoms are the smallest particles of matter, and envisioned them as hard solid spheres. -
JJ Thomson
Thomson lived in the UK from 1856 to 1940. He discovered the electron with cathode ray tube. He showed that the cathode rays were negatively charged. The atomic model at the time didn’t account for negatively and positively charged atoms. For his tremendous work Thomson was award the Nobel Peace Prize in 1906. -
Plum Pudding Model
Proposed by JJ Thomson that the atom is composed of electrons surrounded by positive charges trying to balance out the negative charges. Although this was disproved 5 years later. -
Albert Einstein
Einstein was born in Germany in 1879 but died in New Jersey in 1955. His theory of relativity is built on the idea that only relative motion can be measured. He established law of mass-energy equivalence. E=mc². Einstein also proved the existence of atoms. Einstein proved this by still using a perfectly still cup of water. Considered one of the greatest minds ever and his research opened up our eyes to the world. His efforts were appreciated by his 1921 Nobel Peace Prize. -
Nuclear Model
Discovered by Ernest Rutherford.The model stated that an atom contains 3 pats which are the protons, electrons, and neutrons. The foil experiment proved this because as light passed through some particles bounced off differently than others which came from the nucleus. -
Ernest Rutherford
Ernest Rutherford was born in New Zealand in 1871. He did his research in Cambridge where he lived until 1937. Rutherford was a student of JJ Thomson. Discovered that the atom had a nucleus. Rutherford figured out that the negatively charged particles are on the outside while the small dense positively charged particles are on the inside. Founded the famous experiment where he used foil to see how light particles passed through it. He was awarded with his efforts with a 1908 Noel Peace Prize. -
Niels Bohr
Bohr lived in Denmark from 1885 until 1962. He discovered electrons travel in different orbits. Combined theories together in order to prove his Bohr Model. His work in physics earned him a Nobel Prize in 1922 -
Bohr Model
Proposed by Niels Bohr, it was a modification of Rutherford Model. Electrons orbit the nucleus in orbits that have a set size and energy. The energy of the orbit is related to the size. The smaller the orbit the less energy there is. Radiation is absorbed or emitted when an electron moves from one orbit to another. -
Max Planck
Planck was born in Germany in 1858 and lived until 1947. Planck's law states the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature. Basically it describes the strange behavior of the particles that make up our universe. Planck used apparatuses and equations together to make sense of his theory. His work won him the Nobel Prize in 1918. -
Werner Heisenberg
Lived In Germany from 1901-1976. One of the key pioneers of quantum mechanics. Won the Nobel Prize for the creation of quantum mechanics(Basically a theory of the microscopic world and its atoms). He developed the uncertainty principle which stated that the position and velocity of an object cannot be measured at the same time even in theory. He founded his theory through a thought experiment. Heisenberg won a Nobel Peace Prize in 1932. -
Quantum Model
This model was proposed by Erwin Schrodinger. This model helps describe the chance of finding an electron. The model is based of probability as opposed to certainty. -
Erwin Schrodinger
Erwin Schrodinger lived in Austria from 1887-1961. He took the Bohr Model one step further and used equations to find the likelihood of finding an electron in a given position. This helped him earn a share on the 1933 Nobel Peace Prize -
James Chadwick
Won a Nobel Prize for discovery of the neutron. Lived in Germany and in England from 1891 and 1974. Conducted experiments even while in a prison camp during WW1. Was advised by Ernest Rutherford. Discovered that the nucleus of the atom also has a non electric charged neutron. -
Robert Oppenheimer
Oppenheimer lived in New York from 1904 until 1967. He is considered the father of the atom bomb. Oppenheimer along with others were part of the Manhattan project. After the bombs were dropped he criticized his own work and resigned. -
Bibliography
“Democritus.” The History of the Atom, thehistoryoftheatom.weebly.com/democritus.html.
Lavoisier, chemed.chem.purdue.edu/genchem/history/lavoisier.html.
Development of the Atomic Theory, www.abcte.org/files/previews/chemistry/s1_p5.html.
elmenstine, Anne Marie, and Helmenstine. “What Is the Bohr Model of the Atom?” ThoughtCo, www.thoughtco.com/bohr-model-of-the-atom-603815. -
Bibliography 2
“James Chadwick.” Atomic Heritage Foundation, 20 Oct. 1891, www.atomicheritage.org/profile/james-chadwick.
“WERNER HEISENBERG.” Werner Heisenberg - Important Scientists - The Physics of the Universe, www.physicsoftheuniverse.com/scientists_heisenberg.html.
