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Democritus (460 B. C.)

Democritus was a Greek philosopher who is credited for the conception of the idea of the atom

Democritus was a Greek philosopher so he was known for thinking outside the box. This was important when he came up with the idea of atomos (meaning really tiny) this came from his idea that if you were to infinitely cut something in half, you would eventually find something that isn't divisible. His idea wasn't thought about and was heavily crityisized for many years, until Dalton expanded it further.

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J. J. Thomson (1856-1940)

J. J. Thomson was born December 18th, 1856, Cheetham Hill, Manchester, United Kingdom

Thomson is best known for his discovery of the electron and his model of the atom, the Plum Pudding model, which had electrons floating around in a field of positive energy, like an atomic fruit cake. Before Thomson’s discovery people and scientists believed that the atom was a sphere, with no electrical charge. Thomson proved this wrong with his cathode ray experiments. He created a beam of charged energy by running an electric current through two oppositely charged electrodes. To test the charge of this beam he had it run through two opposingly charged magnets. He noticed that the beam would turn away from the negatively charged magnet and towards the positively charged magnet, indicating negatively charged particles. This finding lead Thomson to believe that the atom was still a sphere, just with a mix of positive and negative charges (resulting in an overall neutral charge). We know now that this isn’t true, however it lead to the understanding that atoms are composed of negative and positive charges.

Thomson recieved a Nobel Prize for his discovery of the election in 1908. He also did work with cathode rays and discovered that they interact with magnetic fields. His mathematical publishings laid the groundwork for the current understanding of electromagnetism.

Discovery of the electron and nucleus. (n.d.). Retrieved from https://www.khanacademy.org/science/chemistry/electronic-structure-of-atoms/history-of-atomic-structure/a/discovery-of-the-electron-and-nucleus.

Helmenstine, A. M. (2019, July 8). J.J. Thomson Biography: The Man Who Discovered the Electron. Retrieved from https://www.thoughtco.com/j-j-thomson-biography-607780.

J.J. Thomson Facts. (n.d.). Retrieved from http://www.softschools.com/facts/scientists/jj_thomson_facts/1605/.

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Ernest Rutherford (1871-1937)

Rutherford was born on August 30th, 1871 in Brightwater, New Zealand

 Rutherford disproved the Plum Pudding model set in place by J.J. Thompson which claimed that the atom was comprised of electrons floating around in a positive field, neutralizing the atom. Rutherford’s experiments had a few of the alpha rays deflect away from the gold foil they were shot at, rather than passing right through as the plum pudding model would have predicted. Rutherford’s experiment’s results lead him to the conclusion that the atom has a single dense center (the nucleus) and the electrons fly around in orbitals. Rutherford’s model, while somewhat accurate, still left some things to be desired. For example, it didn’t explain why the negatively charged electrons didn’t just fall towards the positively charged nucleus. Rutherford made his discovery while doing his gold foil experiment. This had him shoot an alpha particle ray at a piece of gold foil. He was able to notice that while many alpha particles did pass through the foil (as expected) a few bounced off in other directions, which was not expected. 

Rutherford won a Nobel prize for his work in the study of disintegrating elements and the chemistry of radioactive substances in 1908. He made many discoveries in science, including the discovery of alpha and beta particles, the discovery and prediction of the neutron, and accurately estimating the age of the Earth using radiometric dating. He was also knighted and reached the role of baron before his death. 

Ernest Rutherford. (2018, January 11). Retrieved from https://www.sciencehistory.org/historical-profile/ernest-rutherford.

The Nobel Prize in Chemistry 1908. (n.d.). Retrieved from https://www.nobelprize.org/prizes/chemistry/1908/summary/.

Home. (n.d.). Retrieved from https://www.famousscientists.org/ernest-rutherford/.

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Niels Bohr (1885-1962)

Niels Bohr was born on October 7th, 1885 in Copenhagen, Denmark

Bohr is responsible for coming up with the Bohr model of the atom. Basically, electrons orbit around the nucleus of the atom in fixed orbitals. However, electrons can jump between these orbitals when they gain or lose energy (which is seen as protons). This model of the atom helped explain the stability problems the previous model had difficulty with. The previous model had electrons orbit the nucleus but because atoms release electromagnetic radiation (photons) the electrons would lose energy and should theoretically fall into the nucleus. The Bohr model explained that since electrons are able to jump in and out of energy orbitals they would never get close enough to crash into the nucleus. Bohr proved his model by proving the stability of the atom while having electrons stay in orbital formations.

Bohr won a Nobel prize for his updated model of the atom in 1922. During the Nazi occupation of Denmark, Bohr spent time in the U.S. and England working on the Manhattan Project and Atomic Energy Project. While there he spent time with many of the other founding fathers of the modern understanding of atomic theory. Like Rutherford and J.J. Thompson

(n.d.). Retrieved from http://abyss.uoregon.edu/~js/glossary/bohr_atom.html.

The Nobel Prize in Physics 1922. (n.d.). Retrieved from https://www.nobelprize.org/prizes/physics/1922/bohr/biographical/.

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Erwin Schrodinger (1887-1961)

Schrodinger was born in Austria on August 12th, 1887

Schrodinger came up with mathematical formulas that could predict where an electron would be at a certain time. His calculations would predict the odds of where an electron would be. He described the path of electrons as waves and would describe regions of space as orbitals. These orbitals would be where electrons are most likely to be found. He found the electrons existed in a space called the electron cloud, away from the nucleus. Schrodinger used equations rather than experiments to make his discovery. 

Schrodinger is referred to as the father of quantum physics, however, his 1944 book “What is Life?” inspired other scientists in the fields of molecular biology and genetics to pursue those fields, and eventually lead to the discovery of the structure of DNA

Home. (n.d.). Retrieved from https://www.famousscientists.org/erwin-schrodinger-2/.

(n.d.). Retrieved from http://abcte.org/files/previews/chemistry/s1_p6.html.

http://chemed.chem.purdue.edu/genchem/history/schrodinger.html

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James Chadwick (1891-1974)

James Chadwick was a British physicist born on October 20th, 1891. He is most credited for the discovery of the neutron, which was originally theorized by Rutherford, in 1932.

Chadwick found the neutron by shooting beams of alpha-particles at the nuclei of different metals and measuring the nuclear charges of the particles that would come off the metals. When he was studying at the irradiation of beryllium he found that rather than a stream of electromagnetically charged radiation, there was instead a stream of neutral rays. Chadwick found that these particles, which he dubbed neutrons, had a similar mass to that of the proton.

Chadwick won a Noble prize for his discovery in 1935. His knowledge about the neutron lead him to become a lead scientist on the Manhattan project, giving way to the production of the nuclear bomb.

Brown, A. (1997).The neutron and the bomb: a biography of Sir James Chadwick. Oxford: Oxford University Press.