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500 BCE
The Alchemists
The alchemists focused mainly on turning regular objects into something more valuable, mainly gold. They were never successful in creating gold but a German alchemist named Hennig Brandt thought he could turn urine into gold. During his attempt, he boiled urine down into a paste and exposed it to intense heat. This didn't create gold but it lead to the accidental discover of phosphorus. -
492 BCE
Democritus
Democritus discovered how atoms combine with each other and how they are arranged. -
450 BCE
Aristotle
The only thing Aristotle discovered that caries on to the modern atomic theory is the fact that there are elements -
423 BCE
Plato
Plato introduced the atomic theory in which atoms form together in geometric shapes to create elements. -
Robert Boyle
Robert Boyle discovered that the volume of a gas varies inversely with pressure. This is later known as the Boyle's law. The volume of a gas decreases with increasing pressure and vice versa. -
Lavoiser
He recognized and named oxygen in 1778 and hydrogen in 1783, and opposed the phlogiston theory. Lavoisier helped construct the metric system, wrote the first extensive list of elements, and helped to reform chemical nomenclature -
Solid Sphere of "Billiard Ball" Model
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John Dalton
John Dalton was an English chemist, physicist, and meteorologist. He is best known for introducing the atomic theory into chemistry, -
Dmitri Mendeleev
He is best remembered for formulating the Periodic Law and creating a farsighted version of the periodic table of elements. -
J. J. Thomson
J.J. Thomson was credited with the discovery of the electron, the first subatomic particle to be discovered -
The Curies
The Curies discovered the new element 'radium'. The name comes from the Latin word radius, meaning 'ray'. -
"Plumb Pudding" Model
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Albert Enstein
Albert Einstein mathematically proved the existence of atoms, and thus helped revolutionize all the sciences through the use of statistics and probability. -
Robert Millikan
He was an American experimental physicist honored with the Nobel Prize for Physics in 1923 for the measurement of the elementary electric charge and for his work on the photoelectric effect. -
Ernest Rutherford
Ernest Rutherford postulated the nuclear structure of the atom, discovered alpha and beta rays, and proposed the laws of radioactive decay. -
Neils Bohr
Neils Bohr is the first to discover the atomic model. He found that electrons circle around the positive charged nucleolus and electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element. -
Solar System Model
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Henry G. J. Mosely
Moseley's experiments proved that the major properties of an element are due to its atomic number. He firmly established the relationship between the atomic number of an element and the charge of its nucleus. -
Werner Heisenberg
Werner Heisenberg discovered a way to formulate quantum mechanics in terms of matrices. -
Electron Cloud Model
