Timeline of Atomic Theory

Timeline of Atomic Theory

Democritus400BC

J. J. Thomson1897AD

John Dalton1808AD

Ernest Rutherford1909AD

Neils Bohr1913AD

Robert Millikan1907AD

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Atomic Theoryall atoms:-are small, hard particles-are made of a single material in different shapes and sizes-are always moving-create different materials by joining together

Atomic Theory -all matter is composed of atoms-atoms of all elements are the same size, mass, etc.-atoms of different elements are different -atoms cannot be divided

Discoveries-electron (Cathode Ray Experiment 1897)-plum pudding model (1904)-isotopes (1913)

Discoveries-protons are surrounded by negatively charged electrons-most of the atom is empty space-most of the mass is in the nucleus-the nucleus is made up of positively charged protons-Rutherford Model(Gold Foil Experiment 1909)

Discoveries-all electrons are negatively charged-proved Thomson's theory on the size of an atom(Oil Drop Experiment)

Discoveries-electrons move in specific layers (not randomly)-atoms absorb or give off energy when electrons move levels-Onion Model