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440 BCE
Plato
Plato's atomic theory is that solid forms of matter are composed of indivisible elements shaped like triangles. -
400 BCE
Democritus
Democritus' theory stated that all matter was solid, hard, and indestructible. It moved in infinite numbers through empty space until it stopped. -
Robert Boyle
Robert Boyle believed that everything was composed of very tiny particles -
The Alchemists
The Alchemists believed all metals were formed from two principles- mercury and sulfur -
Antoine Lavoisier
Lavoisier's theory was the law of conservation of mass explaining how matter is conserved by chemical changes. -
John Dalton
John Daltons atomic theory stated that all matter is made of atoms and all atoms of a given element are identical in mass and properties. -
Billiard Ball Model
The Billiard Ball Model, discovered by John Dalton, is an atom defined as a ball-like structure, as the concept of atomic numbers. -
Amedeo Avogadro
He discovered that equal volumes of gases at the same temperature and pressure contain the same number of molecules. -
Dmitri Mendeleev
He discovered that elements arranged according to the value of their atomic weights present clear periodicity properties. -
JJ Thompson
JJ Thompson believed that all atoms contain tiny negatively charged subatomic particles. -
Pierre and Marie Curie
Pierre and Marie Curies' atomic theory was that powerful rays, or energy, gave off tiny particles from tiny atoms that were disintegrating inside elements. -
Plum Pudding Model
The Plum Pudding Model, discovered by JJ Thomson, depicts the electrons as negatively charged particles embedded in a sea of positive charge. -
Albert Einstein
Einstein's atomic theory states that any liquid is made up of molecules. -
Robert Millikan
He believed that electrons had a discrete, quantifiable change compared to other subatomic particles. -
Ernest Rutherford
Ernest Rutherford described the atom to have a tiny and dense positively charged core called the nucleus. -
Neils Bohr
Neils Bohr's theory on hydrogen atoms, based on quantum theory, explains that some physical quantities only take discrete values. -
Solar System Model
The Solar System Model, discovered by Neils Bohr, is atoms consisting of a number of electrons in orbits around the nucleus. -
Henry G.J. Mosely
Henry discovered that atomic numbers are the fundamental feature that describes an element. -
Erwin Schrodinger
Erwin's theory states that the behavior of electrons within atoms could be explained by treating them mathematically as matter waves. -
Electron Cloud Model
The Electron Cloud Model, discovered by Erwin Schrodinger, is the area around an atom's nucleus where electrons are likely to be found. -
James Chadwick
James Chadwick contributed to the atomic theory by discovering the neutron.