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400
400 BC: Democritus
Has the theory that everything around him was made out of atoms. -
Isaac Newton
Proposes theory that that there is a mechanical universe with small solid masses moving. -
John Dalton
Proposed an 'Atomic Theory' with sphere-shaped soild atoms based on properties of mass. -
Micheal Faraday
Studied the effect of electricity on solutions. Developed laws of electrolysis -
Dimitri Mendeleev
Arranged all the elements into 7 different groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights". This became known as the Periodic Law. -
G.J. Stoney
His theory was that electricity was made of negative particles he called 'electrons'. -
J.J Thompson
Used a CRT (Cathode Ray Tube) to experimentally determine the charge to mass ratio of an electron. -
J.J. Thompson
He studied Canal Rays and found they were associated with the proton H. -
Marie Sklodowska Curie
She studied Uranium and thorium and called their decay process 'radioactivity'. She and her husband also discovered the elements polonium and radium. -
Soddy
He called the disintegration of radio elements into variants he called 'isotopes' or totally different elements. Also, discovered 'half-life' -
Rutherford
He studied the radiations from uranium and thorium and named them alpha and beta. -
Niels Bohr
Developed an explanation of atomic structure that talks about the regularities of the periodic table of elements. His atomic model had atoms built up of sucessive orbital shells of electrons. -
James Chadwick
He used Alpha particles to discover a neutral atomic particle with a mass close to a proton. This was the neutron.