Atomic Model Timeline

The Alchemists

500 BCE

The alchemists were the first to use the word "element". They analyzed matter and how it forms to a chemical reaction. They also attempted to purify, mature, and perfect certain metals.

Democritus

460 BCE

Democritus's atomic theory was that an atom was just one sphere.

Plato

440 BCE

Plato (and Aristole) proposed that matter was continuous, infinite, present in every form, and always around it.

Robert Boyle

1662

Robert Boyle believed that everything was composed of very tiny particles.

Antoine Lavoisier

1777

Antoine Lavoisier discovered the Law of Conversion of Mass, which stated that matter cannot be created or destroyed.

John Dalton

1803

John Dalton discovered how atoms worked and made understanding chemical compounds simple.

Amedeo Avogadro

1811

Amedeo Avogadro hypothesized that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

Dmitri Mendeleev

1869

Dmitri Mendeleev created a basic Period Table of Elements.

JJ Thompson

1897

JJ Thompson discovered elements through the Cathode Ray Rube Experiment. He also created the Plum Pudding Model.

Pierre and Marie Curie

1898

The Curies discovered "Polonium", a new element which was 400 times more radioactive than any other

Albert Einstein

1905

Albert Einstein mathematically proved the existence of atoms. His atomic theory revolutionized modern science.

Ernest Rutherford

1911

Ernest Rutherford performed the Gold Foil Experiment, which made him discover a nucleus present in the atom. He created the Nuclear Model.

Henry G.J. Mosely

1913

Henry Mosely found a link to the atomic number. He developed it into more detail.

Niels Bohr

1922

Niels Bohr created a model which proved that when you excite an electron by giving it energy, it jumps onto another energy level. The electrons, as a result, give off light quantum.

Robert Millikan

1923

Robert Millikan helped in understanding the structure of an atom. He performed the Oil Drop Experiment to find out that electrons were negatively charged.

Werner Heisenberg

1925

Werner Heisenburg contributed to the Atomic Theory through formulating quantum mechanics in terms of matrices and in discovering the Uncertainty Principle, which states that a particle's position and momentum cannot both be known exactly.

Erwin Schrodinger

1926

Erwin Schrodinger theorized that the behavior of electrons within atoms could be explained by treating them mathematically as matter waves.

James Chadwich

1935

James Chadwich discovered neutral charged neutrons in the nucleus.