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500 BCE
The Alchemists
The Alchemists believed all metals were formed from mercury and sulfur, the mercury gave the metal malleability, and the sulfur gave it body and calcination. -
427 BCE
Plato
Plato believed solid forms of matter are composed of indivisible elements shaped like triangles. -
400 BCE
Democritus
Democritus believed atoms were uniform, solid, incompressible, and indestructible, and they moved in infinite numbers through empty space until stopped. -
Robert Boyle
Robert Boyle believed everything was composed of very tiny particles. -
Antoine Lavoisier
Antoine Lavoisier believed that matter was composed of atoms that were not created or destroyed during chemical reactions. -
John Dalton
John Dalton believed elements consisted of invisible small particles, all atoms of the same element are identical, and atoms can neither be created or destroyed. -
Billiard Ball Model
John Dalton envisioned atoms as solid, hard, spheres, like billiard balls and used wooden balls to model them. -
Amedeo Avogadro
Amedeo Avogadro believed equal volumes of gases at the same temperature and pressure contain equal numbers of molecules regardless of their chemical nature and physical properties. -
Dmitri Mendeleev
Dmitri Mendeleev believed elements arranged according to the value of their atomic weights present a clear periodicity of properties. -
Pierre and Marie Curie
Pierre and Marie Curie suggested that the powerful rays, or energy, the polonium and radium gave off were actually particles from tiny atoms that were disintegrating inside the elements. -
Plum Pudding Model
The plum pudding model shows the electrons were embedded in a uniform sphere of positive charge, like blueberries stuck into a muffin. -
Albert Einstein
Albert Einstein believed any liquid is made up of molecules, that are always in random, ceaseless motion. -
Robert Millikan
Robert Millikan believed electrons did have a discrete quantifiable charge -
Ernest Rutherford
Ernest Rutherford believed atoms have a tiny, dense, and positively charged core called the nucleus -
Niels Bohr
Niels Bohr believed that electrons moved around a nucleus, but only in prescribe orbits, and if electrons jump to a lower-energy orbit, the difference is sent out as radiation. -
Henry G. J. Moseley
Henry Moseley believed atomic numbers are the fundamental feature that describes an element. -
Solar System Model
The solar system model describes atoms as consisting of a nucleus with a number of electrons in orbit around the nucleus. -
Electron Cloud Model
The electron cloud model represents the area around and atom's nucleus where electrons are most likely to be found. -
James Chadwick
James Chadwick discovered the Neutron, which is a subatomic particle with no electrical charge. -
JJ Thomson
JJ Thomson believed all atoms contain tiny negatively charged subatomic particle or elements