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Don't worry! This is not the end of the Atomic Theories and Atomic Models Timeline!

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Erwin Schrödinger, (born August 12, 1887, Vienna, Austria—died January 4, 1961, Vienna), Austrian theoretical physicist who contributed to the wave theory of matter and to other fundamentals of quantum mechanics.

Schrödinger combined the equations for the behavior of waves with the de Broglie equation to generate a mathematical model for the distribution of electrons in an atom.

Erwin Schrödinger showed that the quantization of the hydrogen atom’s energy levels that appeared in Niels Bohr’s atomic model could be calculated from the Schrödinger equation, which describes how the wave function of a quantum mechanical system (in this case, a hydrogen atom’s electron) evolves.

Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position.

Sources:

http://chemed.chem.purdue.edu/genchem/history/schrodinger.html#:~:text=Erwin%20Schrodinger&text=A%20powerful%20model%20of%20the,of%20electrons%20in%20an%20ato

https://www.britannica.com/biography/Erwin-Schrodinger

https://www.britannica.com/biography/Erwin-Schrodinger

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James Chadwick, in full Sir James Chadwick, (born October 20, 1891, Manchester, England—died July 24, 1974, Cambridge, Cambridgeshire), English physicist who received the Nobel Prize for Physics in 1935 for the discovery of the neutron.

James Chadwick (1891–1974) in 1932 introduced neutron. He deduced that a neutron is a particle with no electric charge or is “neutral.” So Chadwick refined the Bohr model to include neutrons within the nucleus.

Chadwick discovered that the nucleus also contains neutral particles called neutrons. Soddy demonstrated that atoms of the same element can differ in mass; these are called isotopes.

Sources:

https://www.britannica.com/biography/James-Chadwick

https://www.msnucleus.org/membership/html/jh/physical/atomictheory/lesson1/atomic1f.html?fbclid=IwAR2LcaJAMXq0sqkWJlV8--Qpp9-skiMTUQTvvETpAU-O9F6ExIh0lkcx18M

https://courses.lumenlearning.com/chemistryformajors/chapter/evolution-of-atomic-theory/?fbclid=IwAR3-pKUh00QnviDZUU_-42JOrjWC6Xdavc7BNv4E8L3BvkIClBCsx1Sy7Wc

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Niels Bohr, in full Niels Henrik David Bohr, (born October 7, 1885, Copenhagen, Denmark—died November 18, 1962, Copenhagen), Danish physicist who is generally regarded as one of the foremost physicists of the 20th century.

In 1913, Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. Electrons should move around the nucleus but only in prescribed orbits. When jumping from one orbit to another with lower energy, a light quantum is emitted.

Sources:

https://www.britannica.com/biography/Niels-Bohr

https://www.msnucleus.org/membership/html/jh/physical/atomictheory/lesson1/atomic1f.html?fbclid=IwAR2LcaJAMXq0sqkWJlV8--Qpp9-skiMTUQTvvETpAU-O9F6ExIh0lkcx18M

https://www.nobelprize.org/prizes/physics/1922/bohr/facts/?fbclid=IwAR2Wc1wNgfetBiNgUU-96ysaG1cjfzXrWut35O_Lf2TxZ3Rkaqq-d9DWHQo

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Ernest Rutherford, in full Ernest, Baron Rutherford of Nelson, (born August 30, 1871, Spring Grove, New Zealand—died October 19, 1937, Cambridge, Cambridgeshire, England), New Zealand-born British physicist considered the greatest experimentalist since Michael Faraday (1791–1867).

In 1907, he returned to England and accepted a position as a professor at the University of Manchester. Rutherford then conducted additional experiments, firing alpha particles at foil, and made the ground-breaking discovery that nearly the entire mass of an atom is concentrated in a nucleus. In doing so, he gave birth to the nuclear model, which paved the way for the invention of the atom bomb and marked the beginning of nuclear physics.

He was dubbed the father of the nuclear age and received the Nobel prize for chemistry in 1908.

Sources:

https://www.britannica.com/biography/Ernest-Rutherford

https://www.biography.com/scientist/ernest-rutherford

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J.J. Thomson, in full Sir Joseph John Thomson, (born December 18, 1856, Cheetham Hill, near Manchester, England—died August 30, 1940, Cambridge, Cambridgeshire), English physicist who helped revolutionize the knowledge of atomic structure by his discovery of the electron (1897). He received the Nobel Prize for Physics in 1906 and was knighted in 1908.

The electron was discovered in 1897 by the English physicist J.J. Thomson during investigations of cathode rays. His discovery of electrons, which he initially called corpuscles, played a pivotal role in revolutionizing knowledge of atomic structure.

Sources:

https://www.britannica.com/biography/J-J-Thomson

https://g.co/kgs/d5mokH

https://www.google.com/url?sa=t&source=web&rct=j&url=https://nationalmaglab.org/education/magnet-academy/history-of-electricity-magnetism/pioneers/joseph-john-thomson%23:~:text%3DA%2520series%2520of%2520experiments%2520with,electrical%2520conductivity%2520of%2520various%2520gases.&ved=2ahUKEwjdv_vI3-7vAhWOvZQKHUfnCnYQFjAEegQIAxAF&usg=AOvVaw1FNKLlObUk-wTENtQM_9d4

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.britannica.com/biography/J-J-Thomson&ved=2ahUKEwi5z4vW3-7vAhVjIaYKHYK5BT4QFjACegQIDRAF&usg=AOvVaw1WxTokIkYk3upkPO4JrnRa

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John Dalton, (born September 5 or 6, 1766, Eaglesfield, Cumberland, England—died July 27, 1844, Manchester), English meteorologist and chemist, a pioneer in the development of modern atomic theory.

John Dalton proposed the following theories:

1. Matter is made of small indivisible atoms.

2. Atoms can’t be subdivided, created or destroyed.

2.1 Atoms of the same element have the same property.

2.2 Atoms of different elements have different properties.

3. Atoms of different elements can form compounds.

Sources:

https://medium.com/@Intlink.edu/a-timeline-of-atomic-models-cb2607b1da85

https://www.britannica.com/biography/John-Dalton

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Democritus, (born c. 460 BCE—died c. 370), ancient Greek philosopher, a central figure in the development of philosophical atomism and of the atomic theory of the universe.

Around 400 B.C.E., the Greek philosopher Democritus introduced the idea of the atom as the basic building block matter. He called these pieces "atomos," which means “uncuttable” in Greek. This is where the modern term atom comes from. He taught that there were substances called atoms and that these atoms made up all material things. The atoms were unchangeable, indestructible, and always existed.

Sources:

https://www.britannica.com/biography/Democritus

https://courses.lumenlearning.com/cheminter/chapter/democritus-idea-of-the-atom/

https://flexbooks.ck12.org/cbook/ck-12-middle-school-physical-science-flexbook-2.0/section/3.11/primary/lesson/democrituss-idea-of-the-atom-ms-ps

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Did you know that the atomic models change overtime?

The timeline that we made shows the development of the Atomic Theories and Atomic Models over the course of time.

Have fun!