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500 BCE
The Alchemists
Alchemists believed that everything was made up of four elements, which were earth, air, fire, and water. This laid the foundation for the modern Periodic Table of Elements. -
400 BCE
Democritus
Democritus theorized that all matter was made of small indivisible particles. Democritus did not believe in any gods, unlike many other people at the time. -
360 BCE
Plato
Plato theorized that the heavens and objects in the heavens were made of an element called ether. Plato also made significant contributions to philosophy. -
Robert Boyle
Robert Boyle defined an element as a substance that cannot be broken down into more substances. Robert Boyle also researched alchemy. -
Antoine Lavoisier
Antoine Lavoisier came up with the Law of Conservation of Mass, which states that matter cannot be created or destroyed, only changed. Antoine Lavoisier also gave oxygen its name. -
John Dalton
John Dalton used experiments to prove that atoms exist. John Dalton also researched color blindness. -
Billiard Ball Model
The Billiard Ball Model of the atom was one solid particle. There were no subatomic particles. -
Amedeo Avogadro
Amedeo Avogadro proposed that the atoms of elemental gases can be joined together in molecules instead of existing as individual atoms. Amedeo Avogadro was a lawyer before he became a scientist. -
Dmitri Mendeleev
Dmitri Mendeleev created the first periodic table. Dmitri Mendeleev also discovered the Periodic Law. -
J.J. Thomson
J.J. Thomson discovered the electron. J.J. Thomson also proposed the Plum Pudding Model of the atom. -
Pierre and Marie Curie
Pierre and Marie Curie discovered the radioactive elements polonium and radium. Marie Curie is the only person to have won a Nobel Prize in both physics and chemistry. -
Plum Pudding Model
The Plum Pudding Model of the atom was made up of many electrons surrounded by positively charged matter. The Plum Pudding Model did not have a nucleus. -
Albert Einstein
Albert Einstein mathematically proved that atoms exist. Einstein also helped develop the atomic bomb. -
Robert Millikan
Robert Millikan discovered the charge of an electron. Robert Millikan also created anti-submarine technology for the U.S.A. during WWI. -
Ernest Rutherford
Ernest Rutherford discovered that atoms were made up of a nucleus that is surrounded by electrons. Ernest Rutherford is often referred to as the Father of Nuclear Physics. -
Niels Bohr
Niels Bohr discovered that electrons orbit around the nucleus of an atom. Niels Bohr also researched quantum mechanics. -
Henry G.J. Moseley
Henry G.J. Moseley found the atomic number of each element using x-rays. Henry G.J. Moseley was killed during WWI at the age of 27. -
Solar System Model
The Solar System Model of the atom has a nucleus made up of protons and neutrons that is orbited by electrons. The electrons move in set paths around the nucleus. -
Erwin Schrodinger
Erwin Schrodinger created an equation to predict the positions of a particle at a certain time. Erwin Schrodinger also developed the Electron Cloud Model of the atom. -
Electron Cloud Model
The Electron Cloud Model of the atom has a nucleus made up of protons and neutrons that is orbited by electrons. The electrons do not move in set paths around the nucleus. -
Werner Heisenberg
Werner Heisenberg discovered the Uncertainty Principle, which states that the position and momentum of a particle cannot both be known exactly. Heisenberg was awarded the Nobel Prize in Physics in 1932. -
James Chadwick
James Chadwick discovered the neutron. James Chadwick was awarded the Nobel Prize for his discovery of the neutron.
