Atomic Timeline

500 BCE Leucippus

500 BCE

500 BCE
Leucippus Leucippus
Principles/Findings:
- A Space or Void was absolutely necessary for motion to occur
+ Believed to have created the first theory of the atom.

480 BCE Zeno

480 BCE

Principles/Findings:
-Stated that the universe is a single entity.
+Proposed the theory of Eleatics.

465 BCE Democritus

465 BCE

Principles/Findings:
-All matter is consisted of atoms
-Atoms cannot be destroyed
-Atoms cannot be seen.
-Atoms consist of the same parts and structuring
-Atoms are different due to their varying; shapes, masses, positions, and arrangements.
*Solids: Small, pointy Atoms
*Liquids: Large and round Atoms
*Oils: Fine, small Atoms that can slip past each other.
+His contribution to the theory was that he affirmed that the universe is composed of atoms and the void, they are in.

1640 Pierre Gassendi

Aug 25, 1640

Principles/Findings:
- Stated that atoms are solid and lacked in internal structures.
- Believed atoms can form into molecules.
- Atoms had not existed in earths creation.
+ Revived the idea of Atoms.

1704 Isaac Newton

Aug 25, 1704

Principles/Findings:
+Developed an idea regarding a mechanical universe which was driven by an atom.

1789 Antoine Lavosier

Aug 25, 1789

Principles/Findings:
- Believed atoms didn't exist. Countered and contradicted the idea of atoms
- Developed the law of conservation of mass.
+ Allowed for the chemical revolution to take place.

1803 John Dalton

Aug 25, 1803

Principles/Findings:
-Everything is made of atoms. They are both indivisible and are indestructible.
-All atoms' properties are identical in any given element.
-Compounds ate made by combining multiple different types of atoms.
-When a chemical reaction occurs, the atoms are rearranged.
+Dalton is known for discovering the atomic theory.

1832 Michael Faraday

Aug 25, 1832

Principles/Findings:
-Matter is recognized where lines of force met at a particular point in space.
-Did not support the atomic theory.
-Created "Faraday's laws of Electrolysis".
-Altered Dalton's theory.
-Atoms had electrical properties.

1859 J. Plucker

Aug 25, 1859

Principles/Findings:
-First to experiment with electron rays in a vacuum.
+Allowed further research into the atomic theory to occur.

1873 James Clark Maxwell

Aug 25, 1873

Principles/Findings:
- Stated "the void" was filled with electric and magnetic waves.
+ his work allowed for equations from Faraday to be translated.

1897 J.J. Thompson

Aug 25, 1897

Principles/Findings:
- The number of electrons equaled the number of protons while neutrons had no direct match.
- Atoms were spherical in shape.
- The protons are surrounded by electrons.
- Electrons are smaller than atoms.
+ Thomas proved that atoms were composed of protons, neutrons, and electrons. Thomas found electrons.

1898 Rutherford's Gold Foil Experiment

Aug 25, 1898

The gold foil experiment was conducted to test the effect of alpha particles on matter. Rutherford placed a plate of gold foil surrounded by a sheet of sulfide. The gold was used to test whether particles to penetrate, or scatter, around 90 degrees off, they hit the sulfide screen, emitting light; or it may have deflected the beam back. This experiment ended up proving that an atom had a nucleus, and J.J. Thompson's hypothesis for the structure of an atom.

1909 Robert Millikan

Aug 25, 1909

Principals/Findings:
+ Millikan was able to specify and point out the size of an electrons charge.

1911 Ernest Rutherford

Aug 25, 1911

Principles/Findings:
- Atoms possess a nucleus.
- Found the proton.
- Almost all of the atoms mass is concentrated in the nucleus which is a thousand times smaller than the actual atom.
+Unified many concepts in the growing atomic theory, and disproved some as well. He also ended up classifying many different types of rays.

1922 Neils Bohr

Aug 25, 1922

Principles/Findings:
- Electrons travel is only possible on separately expanding orbits.
- Valence shells, can hold more electrons than inner orbits.
- The orbits determined many atoms properties.
- When an electron jumps from an outer orbit to an inner orbit, light is emitted.(calculated with the difference of 2 orbital energies.
+Bohr's explanation of the atom's orbit allowed for the explanation of the different properties of different atoms to be better understood.

1923 Werner Heisenberg

Aug 25, 1923

Principles/Findings:
-Proposed and discovered that it is not possible to know a particles position and velocity at the same time.
+Heisenberg calculated the electrons' behavior and was useful to help clarify the modern view of an atom

1930 Erwin Schrodinger

Aug 25, 1930

Principals/Findings:
- Proposed electrons in orbit create "standing waves".
- Only where the electron could possibly be can be described.
- Waves can be used to describe electrons through atoms.
+Proposed that the mechanics of waves are the actual mathematical method for atoms.

1932 James Chadwick

Aug 25, 1932

Principle/Findings:
- Atoms have neutrons, the neutrons are found in the nucleus.
- Neutrons account for an atoms atomic mass.
+Proved that atom's nuclei were comprised of more than just protons, they were comprised of protons and neutrons. His discoveries also allowed for the advancement of the understanding of atoms' nuclei.

1935 Hans Bethe

Aug 25, 1935

Principles/Findings:
- Found the carbon-nitrogen reaction is the same reaction that gives stars power.
+ Developed the theory of Deuteron. Allowed for a better understanding of atoms in space.

1942 Enrico Fermi

Aug 25, 1942

Principles/Findings:
- Proposed and established the concept of fission.
+ Aided in the creation of the first two atomic bombs that successfully forced the Japanese to surrender and end World War 2.