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460
First Idea of Atoms
In 460 B.C, a Greek philosopher named Democritus develops the idea of atoms. His idea is that if you break a piece of matter in half over and over again, it will eventually be so small that it cannot be broken in half again. He called this tiny piece of matter an atom. -
Lavoisier's Discoveries
Lavoisier created the formula for conservation of matter and discovered the difference between an element and a compound. -
John Dalton
In the 1800's, nearly 2000 years after Democritus' idea, an English chemist named John Dalton did experiments with different chemicals that proved matter was made of lumpy particles. -
First Model of the Atom
In 1897, a physicist named J.J Thomson discovered the electron and created a model for the structure of the atom. He knew that electrons had a negative charge and thought that meant matter had a positive charge. -
Max Planck
In 1900 Max Planck, a theoretical physicist, discovered that when you vibrate atoms hard enough you can measure the energy in units. He called the units "quanta." -
Electron
In the year of 1908, Robert Millikan discovered the electric charge of the electron. -
Ernest Rutherford
In 1909 an English guy named Ernest Rutherford discovered that all the mass of an atom was in a small, positive charged ball in its center. -
The Bohr Atomic Model
A Danish man called Neils Bohr presents the Bohr atomic model. -
The Elements
Glen T. Seaborg identified elements heavier than Uranium and added elements 94 through 102
