Science Atomic Theory

Plato

440 BCE

said that the stars, planets, and the sun are composed of Atoms of ether.

Democritus

400 BCE

said all materials were made of atomos and that each material had its own type of atomos and it would have the same properties as other atomos of its type.

Robert Boyle

1662

proposed that elements are composed of corpuscles of various types and sizes that separate into groups that make different chemical substances.

Antoine Lavoisier

1794

made the law of conservation of matter and begun the conversation of what an atom is.

The Alchemists

1803

accidently started the present day periodic table by trying to make common metals like lead into gold.

John Dalton

1803

proposed all matter is composed of atoms, invisible and indestructible building blocks.

Billard Ball Model

1803

proposed by John Dalton. Said the atom was a hard sphere and had all its components inside of the sphere.

Amadeo Avogadro

1811

said that equal volumes of gas contain equal numbers of molecules and elementry gases are composed of 2 atoms.

Dmitri Mendeleev

1869

said when all chemical elements are arranged by atomic weight then it makes a reoccurring pattern.

JJ Thomson

1897

said all atoms contain electrons which were negatively charged. proposed the plum pudding model.

Pierre and Marie Curie

1898

found strongly radioactive elements such as, polonium and radium.

Plum Pudding Model

1904

proposed by JJ Thomson. said that a ball of positive charge would attract the electrons and the electrons would be like tiny dots in the positive charge.

Albert Einstein

1905

mathematically proved the existence of atoms.

Ernest Rutherford

1911

said the atom is mostly empty space.

Niels Bohr

1913

proposed the theory for the billiard ball structure of the atom.

Solar System Model

1913

proposed by Niels Bohr. There are rings of electrons around a nucleus just like a planet and its moons.

Robert Millikan

1913

found out about the electron's properties and its mass.

Henry G. J. Mosely

1914

said the atomic number is the number of positive charges in the atomic nucleus.

Erwin Schrodinger

1926

made an equation that showed the energy level of certain atoms.

Electron Cloud Model

1926

proposed by Erwin Schrodinger and is the modern version of the atom. said that the nucleus of the atom was surrounded by a cloud of electrons.

Werner Heisenberg

1927

proposed the uncertainty principle. Particles are moving constantly in random motion and we cannot predict its path.

James Chadwick

1932

said atoms also have neutrons not just electrons and protons.