Science Atomic Model Timeline

The Alchemists

500 BCE

The Alchemists made a theory that sulfer and mercury make up all metals and it is possible to turn base elements into silver or gold. Alchemists were the first to use the word element when talking about chemical reactions.

Plato

428 BCE

Plato said that ideal geometric shapes serve as atoms. For example he thought the Earth was a cube shape.

Democritus

400 BCE

Democritus found out that all atoms are not the same and are always moving. He made a theory to explain why and how atoms were so small. He suggested a much more advanced atomic theory.

Robert Boyle

1640

Robert Boyle proposed that elements are composed of "corpuscles" of sizes and types that can be able to organize themselves into groups that represent different chemical substances.

Antoine Lavoisier

1777

Antoine Lavoisier created the first version of the Law of Conservation of Matter. He also named oxygen and hydrogen. He invented the first periodic table which included 33 elements.

John Dalton

1803

John Dalton said that all matter is made up of atoms. He also prepared the atomic theory. He found atomic weight and made chemical symbols. John Dalton made the most useful atomic theory of matter.

Billiard Ball Model

1803

The Billiard Ball Model was created by John Dalton and stated that all elements are composed of atoms and it is impossible to divide or destroy an atom. Dalton envisioned atoms as solid, hard spheres like a billiard ball.

Amedeo Avogadro

1811

Amedeo Avogadro wrote a paper with two hypotheses. The first hypothesis was that equal volumes of gas contain equal numbers of molecules and the second hypothesis was that elementary gases such as hydrogen, nitrogen, and oxygen were composed of two atoms.

Dmitri Mendeleev

1869

Dmitri Mendeleev created the basic periodic table of elements.

Plum Pudding Model

1897

The Plum Pudding Model was created by J.J. Thomson and stated that the atom was a sphere of positive electricity with negative particles throughout.

J.J. Thomson

1897

J.J. Thomson found electrons and subatomic particles. He found electrons by accident, he was working with electricity and glass tubes but he messed up the experiment which led him to find out about electrons.

Pierre and Marie Curie

1898

Pierre and Marie Curie picked up Becquerel's work on uranium which lead them to discover the elements radium and polonium. Marie Curie said that elements that were exposed to radioactivity over time disintegrate. Pierre Curie said that atoms may be made up of smaller things.

Albert Einstein

1905

Albert Einstein found out nature and matter intertwine somehow and the theory of measurements come from this idea. Einstein published 5 papers on electron and proved the existence of atoms mathematically.

Robert Millikan

1908

Robert Millikan was determined to find the electrical charge of electrons. He measured water droplets and failed, but retried his experiment with oil droplets which succeeded and proved that electrons are negatively charged.

Ernest Rutherford

1911

Ernest Rutherford created and tested an experiment based off others that helped him discover the atomic nucleus. The experiment was given the name of the Rutherford Experiment where he used a thin foil made of gold metal to find positive and negative charges in an atom.

Niels Bohr

1913

Niels Bohr figured out the structure of an atom. He introduced Electrons for the first time in a book that he wrote based on the structure of an atom. He also created the basis of the quantum theory.

Henry G.J. Mosely

1914

Henry G.J. Mosley discovered the number of protons in an element and each of their atomic numbers.

Electron Cloud Model

1920

The Electron Cloud Model was created by Erwin Schrodinger and Werner Heisenberg. The model showed that the atom is made up of a dense nucleus with many neutrons and protons within it that were then surrounded by electrons. Also stated that all atoms have different energy levels and charges.

Solar System Model

1922

The Solar System Model was created by Ernest Rutherford and Niels Bohr. Rutherford said that the atom is a mostly empty space with a nucleus that has a positive charge surrounded by negative electrons. Bohr added on and said that the negative electrons circulate the atom.

Werner Heisenberg

1925

Werner Heisenberg developed a quantum mechanic based on matrices that sets limits for how precise the position and velocity of a particle can be.

Erwin Schrodinger

1926

Erwin Schrodinger wrote papers on wave mechanics which led to his discovery of quantum mechanics. In order for him to find these theories he worked each of them out in math equations and used statistics to help.

James Chadwich

1932

James Chadwich discovered that the neutron existed. He found this out by looking at alpha waves which bounced off which led him to believe there was no charge in the neutron. This discovery helped him create the atomic bomb, fission, and Uranium.