progress in the atomic theory

Democritus

430 BCE

Democritus came up with the idea of the atom. He contributed to the atomic theory by stating that all matter has atoms, they are too small to be seen, and they are all indestructible

Plato

387 BCE

Plato said that atoms could break down into triangles. He contributed to the atomic theory by helping us understand that elements could be broken down.

The Alchemists

1500

The Alchemists discovered that there are not only the Aristotelian elements, but also other elements like mercury and sulfur. They contributed to the atomic theory by establishing that all matter consists of atoms that cannot be divided.

Robert Boyle

1662

Robert Boyle established Boyle's Law. He contributed to the atomic theory by establishing that is an element is truly and element, it has to be proven to be separable from other substances.

Antoine Lavoisier

1789

Antoine established the Phlogiston Theory. He contributed to the atomic theory by The Law of Conservation of Mass. This theory stated that no mass is lost in a chemical reaction.

Billiard Ball Model

1803

This model was made by John Dalton. The Billiard Ball Model states that atoms are small, undestroyable objects. It also states that atoms of different elements have different weights and properties.

John Dalton

1804

John Dalton made the first complete attempt to describe all matter. He contributed to the atomic theory by stating that all atoms in an element are the same mass.

Amedeo Avogadro

1811

Amedeo Avogadro helped to revise Dalton's theory. He contributed to the atomic theory by stating that equal volumes of different gasses contain the same amount of molecules.

Dmitri Mendeleev

1869

Dmitri Mendeleev made the periodic table. He contributed to the atomic theory by presenting all of the elements in an easy way to read and understand.

JJ Thomson

1897

JJ Thompson discovered the electron. He contributed to the atomic theory by helping us understand what an electron is in an atom.

Plum Pudding Model

1897

The Plum Pudding Model was made by JJ Thomson. This model states that electrons are in a mass of positive charge to make a neutral atom.

Pierre and Marie Curie

1898

Pierre and Marie Curie studied radioactivity. They contributed to the atomic theory by discovering the element radium.

Albert Einstein

1905

Albert Einstein stated that E= mc^2. He contributed to the atomic theory by stating that energy and mass are interchangeable, and they are different forms of the same thing.

Robert Millikan

1910

Robert Millikan determined the magnitude of the electron charge. He contributed to the atomic theory by demonstrating the atomic structure of electricity.

Ernest Rutherford

1911

Ernest Rutherford established the Rutherford Model. He contributed to the atomic theory by establishing the groundwork for the structure of an atom.

Henry G. J. Mosely

1912

Henry G. J. Mosely joined Rutherford's research group. He contributed to the atomic theory by creating an atomic battery while trying to put electrons in a radioactive source.

Neils Bohr

1913

Neils Bohr was a Danish physicist and philosopher. He contributed to the atomic theory by stating that electrons could only be in certain orbits due to the quantum of action.

Solar System Model

1913

This Model is also called the Bohr model, as it was made by Neils Bohr. This model states that atoms are like small solar systems, although it may be wrong.

Electron Cloud Model

1926

This model was made by Ernest Rutherford. The electron cloud model shows the location of electrons in an atom. This model helps us to determine the orbital, or where electrons are found.

James Chadwich

1932

James Chadwich discovered the neutron. He contributed to the atomic theory by deepening our knowledge of the atom and its structure.