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440 BCE
Plato
Plato theorized that these solid forms of matter are composed of indivisible elements shaped like triangles. -
400 BCE
Democritus
Democritus introduced the idea that an atom is the basic building block of matter. -
700
The Alchemists
They found that all metals were formed from 2 principles, mercury and sulfur. -
1543
Solare System Model
The Solar System model shows electrons that are arranged in concentric circular orbits around the nucleus. -
Robert Boyle
Robert Boyle demonstrated that matter is made of tiny particles that he called corpuscles, but today they are known as atoms. -
Antoine Lavoisier
Antoine Lavoisier defined the law of conservation of mass. -
John Dalton
John Dalton suggested that all matter comprimised of indivisible and indestructable atoms withdistinct masses properties -
Billiard Ball Model
John Dalton refers to an atom as the billiard ball, because it is shaped like a ball and at this time they didn't know what was inside it. -
Amedeo Avogadro
Amedeo Avogrado found that volumes of gases at the same temperature and pressure contain the same number of molecules regardless of their chemical nature and physical properties. -
Dimitri Mendeleev
Dimitri devised the periodic classification of the chemical elements. -
JJ Thompson
JJ Thompson proposed the plum pudding model of the atom. -
Pierre and Marie Curie
Pierre and Marie discovered strong radioactive elements like polonium and radium. -
Plum Pudding Model
The Plum Pudding Model negatively-charged electrons embedded within a positively charged "soup." -
Robert Millikan
Robert Millikan had accurate determination of the charge carried by an electron. -
Ernest Rutherford
Ernest Rutherford established that the mass of an atom is concentrated in its nucleus. -
Niels Bohr
Niels Bohr proposed another model of an atom in which the electron is able to occupy only certain orbits around the nucleus. -
Henry G. J. Mosley
Henry reported that frequencies are proportional to the squares of whole numbers that are equal to the atomic number plus a constant. -
Albert Einstein
Albert Einstein mathematically proved the existence of atoms. -
Werner Heisenberg
Werner Heisenberg formulated quantum mechanics in terms of matrices and in discovering an uncertainty principle. -
Erwin Schrödinger
Erwin Schrödinger generated a mathematical model the distributions of electrons in an atom. -
Electron Cloud Model
Erwin Shrödinger used to describe the behavior electrons, it's useful in building a model of atom. -
James Chadwick
James Chadwick discovered the neutron.