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465 BCE
Democritus
Created the first atomic theory. He stated everything is made of tiny indivisible, indestructible atoms. -
400 BCE
Plato
Plato created the atomic theory based on ideal geometric forms that serve as atoms. He thought atoms were composed of individual elements shaped like triangles. -
500
The Alchemists
Believed everything is made up of atoms. Said atoms are Invisible indivisible spheres of matter of an infinite type and number. -
Robert Boyle
Stated that the volume of gas decreases with increase in temperature and pressure and vice versa. This was created a Boyle's law. -
Antone Lavoisier
Stated the law of conservation of mass. Mass is not created or destroyed in chemical reactions. Oxygen is key element in respiration and combustion. -
Billiard ball model
Defined atom to be ball like structure. Made of the electrons moving around the nucleus. -
John Dalton
Stated all matter is composed of atoms relative atomic wastes of 6 elements. He depicted atoms as ball like figures created billiard ball model. -
Amadeo Avogadro
Claimed all volumes of all gases at the same temperature and pressure contain the same amount of molecules. -
JJ Thompson
Discovered the electron. Suggested model of atom as a sphere of positive matter. -
Pierre and Marie Curie
They found radioactive particles casue atoms to break down chemically.They discovered radium and polonium. -
Plum pudding model
Accounted for two properties of the atom not 3. The electrons and protons positive and negative charges. -
Albert Einstein
Mathmatically proved teh existence of atoms. Says any liquid is made of molecules and are always in a ceaseless motion. -
Ernest Rutherford
He proposed the planatary model. It showed the electrons orbiting the central nucleus of the atom. -
Robert Millikan
He verified the existence of atoms. He measured the charge of the electron and verified Einsteins prediction of the relationship between light frequencies and electron energy. -
Neils Bohr
Created the planet model of the atom. He created the model where the electrons orbit the central nucleus. -
Solar system model
Describes how electrons orbit the nucleus. Shows protons electrons and neutrons. -
Henry G.J Mosely
Discovered the atomic number of positive charges of the atomic nucleus. He experimented with x-rays of certain periodic table metals. -
Electron cloud model
The model shows an electron cloud with a central nucleus. Describes the wave like motion of an electron. -
Erwin Shrodinger
Created the quantum mechanical model (electron cloud model). He proposed that atoms moved in waves where their exact position cannot be located. -
James Chadwich
Discovered teh nuetron. He found the neutron by bobarding beryllium with alpha chemicals helping him find the nuetron. -
Dmitri Mendeleev
Created the periodic table of elements. He also created the periodic law. This helped classify elements easy.