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400
Democritus
Matter is made of invisible particles called atoms. -
John Dalton
Proposed an atomic theory with the spherical sold masses in motion. -
Wilhelm Roentgen
Discovered the x-ray. -
X-ray
First x-ray was discovered. -
J.J Thomson
Described that atom as a ball of positive charge containing a number of electrons. *Discovered the electron -
Marie Curie
Discovered polonium. -
Ernest Rutherford
Created the "gold foil" experiment to determine that the nucleus of the atom is very dense and has a positive charge. Assumed electrons were outside the nucleus of the atom. -
Neils Bohr
Explained the atomic structure of the atom as "succesive orbital shells of electrons." Model known as Bohr Planetary Model. -
Scrodinger
Identified that electron cloud model as the probable location of moving electrons. -
Chadwick
Discovered a particle within the nucleus that has a mass simillar to that of a proton. *Discovered the proton. -
Cockroft/Walton
Split the atom. -
Build the atomic bomb
Bomb was dropped on Japan to end World War 2. -
First SNAP-3A
SNAP-3A fueled with polonium, provided power to a satellite radio transmitter. President Eisenhower peace message was broadcast via satellite containing a radio transmitter powered by the SNAP-3A.