-
400
BC Democritus
Greek philosopher named Democritus was the first to discover that the smallest thing that could not be cut was an atom or as he called it atomos meaning "not able to be divided." -
Period: 400 to
Atomic Theory
-
422
BC Aristotle
Greek philosopher Aristotle diagreed with Democritus, he thought that substances were made of the four elements. Eventually his idea was proven incorrect. -
John Dalton
Dalton's idea stated that all matter is made up of atoms and that atoms cannot be created, divided, or destroyed. He also thought that all atoms of a certain element are identical, and if you join atoms of different kinds that it will make a new substance. -
J.J. Thomson
Thomson gave evidence that atoms are made up of even smaller particles. He found negitivley charged particles within the atom. He thought that an atom was a positive sphere with electrons thoughout it. -
Ernest Rutherford
Rutherford did an expirement to study the parts of an atom. His expirement showed that atoms have a nucleus. He later found that the nuecleus is made up of smaller particles. He called the positivley charged particles protons. -
Niels Bohr
Bohr made observations that led to a new theory of how electrons in the atom acted. He agreed with Rutherford's theory, but he added to it. Bohr observed that the elecrtrons move around the nucleus in circular paths. Each path is a certain distance from the nucleus. -
Current Atomic Theory
Democritus is important because he was the one who introduced atoms. Bohr's model of the atom is important because it introduced the idea of the electric cloud.Today the atom is a lot like Bohr's, just a more modified version.
