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440 BCE
Plato
He said atoms must come from triangles, squares, pentagons, etc. -
400 BCE
Democritus
He said matter could be divided into smaller and smaller pieces until the smallest piece was discovered. -
Robert Boyle
He stated that all things are made of atoms and he also created Boyles Law. -
Antone Lavoisier
He said that the total mass of products and reactants in a chemical reaction is always the same. -
The Alchemists
The Alchemists layed down the foundation for the Periodic Table. -
John Dalton
He said that compounds were atoms from different elements combined together. He also proposed the atomic theory -
Amadeo Avagadro
He said that equal volumes of gas contain equal numbers of molecules and that elementary gases such as hydrogen, nitrogen, and oxygen were composed of atoms. -
Dmitri Mendeleev
He discovered of the periodic law and the first periodic table. -
Henry G. J. Mosely
He stated that each element contains a unique number of protons; their atomic number. -
JJ Thompson
He provided the first hint that an atom is made of even smaller particles. -
Pierre and Marie Curie
They discovered 2 elements: polonium and radium. -
Albert Einstein
He mathematically proved the existence of atoms. -
Ernest Rutherford
He stated that atoms are filled with a positively charged material. He theorized that atoms have a small dense positively charged center called nucleus. -
Robert Millikan
He measured the change of an electron using oil droplets. -
Neils Bohr
He stated that the mass of the atom is contained mostly in the nucleus. And that electrons move in orbit around the nucleus. -
Erwin Schrodinger
He formulated a wave equation that calculated the energy levels of electrons in atoms. -
Heisenberg
A particles position and momentum cannot be known exactly -
James Chadwich
He discovered neutrons.