Atomic Timeline-Science Period A

Plato

500 BCE

Plato believed that there were triangles and shapes that were indivisible that made up the "elements" of this time: earth, fire, water, and wind.

Democritus

430 BCE

Democritus made the reasoning that eventually, after cutting down something enough times, they wouldn't be able to be split again and keep the same properties, and those things he called atomos.

The Alchemists

500

The Alchemists started to look at the atomic theory, and the experiments they conducted would help in the process of discovering atoms.

Antoine Lavoisier

1774

Lavoisier discovered that air had what he named oxygen in it, and that water was made up of hydrogen and oxygen.

Billiard Ball Model

1803

This model was proposed by John Dalton, and it theorized that not all atoms were the same, and that all atoms were solid and hard, like billiard balls.

John Dalton

1808

Dalton published a book with his calculations of atomic weights and how the combination of 2 elements results in a set sequence.

Amedeo Avogadro

1811

Avogadro theorized that some simple gases were actually compounds of two or more types of atoms.

Robert Boyle

1861

Boyle supported the idea of seeing the world using particles and how those particles moved. He also defined elements in the "Sceptical Chymist" as things that were unmixed, or unmingled.

Dmitri Mendeleev

1869

Mendeleev came up with, and proposed to the scientific community, the idea for the periodic table of elements.

JJ Thomson

1897

Thomson discovered electrons, and also co-created the "plum pudding" atomic model.

Pierre and Marie Curie

1903

The Curies won the Nobel Prize in Physics for discovering that radiation comes from atoms, and does not depend on how atoms in a molecule are arranged.

Plum Pudding Model

1904

This model was proposed and supported by William and JJ Thomson, and stated that atoms were spheres of positively charged matter, with electrons in it, like plums in a plum pudding.

Albert Einstein

1905

Einstein first mathematically proved that atoms exist.

Ernest Rutherford

1907

Rutherford created one of the first models of what the nucleus in an atom looks like.

Robert Millikan

1910

Millikan accurately determined what the charge electrons in an atom carry.

Niels Bohr

1913

Bohr introduced the idea of electrons orbiting around the nucleus of an atom after learning Professor Rutherford's theories.

Henry G. J. Moseley

1913

Moseley proved that the identity of different elements are determined by the amount of protons in each atom.

Solar System Model

1913

This model was proposed by Niels Bohr, and it theorized that electrons travel in circular motions, or orbits, around the nucleus of the atom.

Werner Heisenberg

1925

Heisenberg theorized that electrons can't be assigned a place in space, or followed in an orbit, because of how randomly they zip around.

Electron Cloud Model

1926

This model was proposed by Erwin Schrödinger, and it theorized that where the cloud of electrons was the most dense, you were more likely to find an electron there.

Erwin Schrödinger

1933

Schrödinger, along with Paul Adrien Maurice Dirac, discovered new forms of the atomic theory.

James Chadwick

1935

Chadwick discovered the neutrons inside of atoms.