Atomic Theory Timeline | Cappy Kuntz

The Alchemists' Contributions

500 BCE

The goal for most alchemists was to either turn other metals into gold or to try to create the philosopher's stone. In their attempts to do so, they broke down the commonly agreed-upon elements of water, earth, fire, and air and discovered several elements. The work of alchemists set the groundwork for modern chemistry and the Periodic Table of Elements. Alchemists still exist today but are extremely rare

Plato's Contribution

427 BCE

Plato was the first to theorize that everything in the universe was made of matter, however, he thought that all the elements were earth, fire, air, water, and cosmos. He also didn't do any testing to support his theory. Plato served as a soldier for a time in ancient Greece.

Democritus's Contribution

425 BCE

Democritus developed the theory of the existence of atoms. Democritus was known as the laughing philosopher.

Robert Boyle's Contribution

1662

Robert Boyle discovered that pressure and volume are inversely proportionate, otherwise known as Boyle's Law. Boyle's father Richard Boyle has been called "the first colonial millionaire".

Antoine Lavoisier's Contribution

1789

Antoine Lavoisier proved the law of conservation of mass which states that matter is not created nor destroyed in a chemical reaction. the mass of the substances before the chemical reaction is the same as the mass of the substances after the chemical reaction. Lavoisier was killed in the Reign of Terror in 1794.

John Dalton's Contribution

1803

John Dalton's atomic theory had four parts;
1. All matter is made of atoms
2. Atoms of the same element have the same mass and properties
3. Compounds are combinations of 2 or more types of atoms
4. Chemical reactions are rearrangements of atoms.
John Dalton first started teaching at the age of twelve.

Amedeo Avogadro's Contribution

1811

Amedeo Avogadro correctly hypothesized that all gases with an equal volume, temperature, and pressure have the same mass.
Amedeo Avogadro had 6 children.

Dmitri Mendeleev's Contribution

1871

Dmitri Mendeleev created the modern Periodic Table of Elements.
Mendeleev also correctly predicted the existence and properties of several elements.

JJ Thomson's Contribution

1897

JJ Thompson discovered the electron. He named his atomic model after the British dessert plum pudding because of how he thought the electrons were spread throughout the positively charged atom.

Pierre and Marie Curie's Contribution

1898

Pierre and Marie Curie discovered the radioactive elements polonium and radium. Because so little was known about radiation, radium was used in many products in the 1910s. Marie Curie's notebook is still highly radioactive to this day.

Albert Einstein's Contribution

1905

Albert Einstein mathematically proved the existence of atoms. He is most well known for his famous theory of relativity.

Ernest Rutherford's Contribution

1911

Ernest Rutherford discovered the nucleus of the atom and that it is only 1/100,000 of the atom's size. Rutherford wrote the entry on radioactivity in the Encyclopedia Britannica for 1910.

Niels Bohr's Contribution

1913

Niels Bohr discovered that electrons travel in separate orbitals and that the number of electrons in the outer orbit defines the element's properties. He also created the solar system atomic model. His University did not have a physics department even though he is a physicist.

Henry G. J. Moseley's Contribution

1914

Henry G. J. Moseley discovered that the atomic number of an atom is the same as the number of positive charges in a nucleus. Moseley was once Ernest Rutherford's assistant.

Robert Millikan's Contribution

1916

Robert Millikan determined the electric charge of electrons in 1910 using his oil-drop experiment. He was the first Ph.D. Graduate of Columbia University's physics department.

Erwin Schrödinger's Contribution

1926

Erwin Schrödinger found a wave equation where if you treat matter as both a particle and a wave, you could find the energy level of an electron. Schrödinger is most well known for the Schrödinger's cat thought experiment.

Werner Heisenberg's Contribution

1927

Werner Heisenberg discovered the uncertainty principle which states that it is impossible to know a particle's exact position and exact momentum. He was captured by U.S. troops for aiding the Nazis in creating a nuclear bomb.

James Chadwick

1932

James Chadwick discovered the neutron in 1932. Chadwick was a prisoner of war during WWI and worked with german scientists.