-
500
Aristotle
-500-400 BC
-Aristotle says that Matter is created by four different elements. The elements being Earth, Fire, Water, and Air. -
500
Democritus
-500-400 BC
-Democritus states that Matter is created by invisible particles called "atoms." -
Period: 500 to
History of the Atom
-
John Dalton
-1600-1700's
-England
-John Dalto is called "The Father of Atomic Theory"
states that :
1. atoms are small hard spheres.
2.atoms are invisible.
3.atoms of the same element are the same.
4.atoms of different elements are different.
5.atoms combine in small whole number ratios. -
J.J Thompson
-1800-1900
-England
-Discovered the electron Cathode Ray Tube. Used the "Plum Pudding" example. -
Ernest Rutherford
-1900's
-England
-Gold Foil Expirament. Discovered the Nucleus.
-Nucleus:very small, very dense. -
Robert Millikan
1908
Chicago
discovered the charge and mass of an electron. -
Niels Bohr
1930's
Denmark
Planetary Model: electrons orbit the nucleus just like planets orbit the sun. -
James Chadwick
-1932
-Cambridge
-discovered the neutron.
