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400 BCE
Democritus
About 400 BC, a Greek philosopher suggested that all matter was formed of different types of tiny discrete particles by breaking up the sea shell -
Antoine Lavoisier
He proposed the law of conservation of matter and through his experiment heating up the mercury he discovered oxygen -
John Dalton
- All matter composed of atoms, indivisible and indestructible building blocks
- All atoms of an element are identical
- Atoms Of different element vary in size and mass
- Compounds are produced through a whole number combination of atom
- Chemical reaction results in rearrangement of atoms in reactants and products compounds.
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J. J. Thomson
He discovered electron by cathode rays tube experiment, he proposed plum pudding model and -
Max Planck
Energy was quantized, quantum theory, energy can be described as an equation E=hv.While he researched blackbody radiation, he kept running to the same problems as the other scientist, until 1900 he discovered the equation explain the test, energy is emitted wavelength, discharge in small packets called quanta -
Marie Curie
the strength of radiation depends only on the amount of uranium or thorium, chemical compound of the same element have different chemical and physical properties,the ability to radiate it must link into the interior of the atom itself, atoms were not invisible by isolated radium and discovered polonium -
Albert Einstein
Proved atoms by the movement of molecules in the liquid caused by the Brownian effect, calculate the size of atoms, analyzed and wrote the mathematical formula to predict the size of both atoms and molecules, laid down the basis for the release of atomic energy, Theory of relativity, He used his theories in quantum physics to explain the photoelectric effect and the brownian motion, atoms did exist -
Ernest Rutherford
He discovered that atoms have a small charged nucleus surrounded by empty space, circled by tiny electrons, Rutherford model ( or planetary model), credited discovery of proton, neutron, elements,radioactive. He did the gold foil experiment. -
Niels Bohr
Atomic model, planetary model, electrons travel in separate orbit, liquid droplets theory, Quantum theory. He expanded Rutherford’s model, that electrons travel only certain successively larger orbit.Outer orbit could not hold -
Robert Milikan
He determined the size of the charge of the electron, electric charge is carried by a single electron by oil drop experiment -
Louis De Broglie
Electrons could behave as a wave under some condition, atoms didn’t behave like a solar system. His research found that in term of physical properties, particles sometimes acted like particles and sometimes acted like wave, the ‘duality’ -
James Chadwick
Discovered neutrons in atom, Alpha particle heat by paraffin wax, measured velocity of proton in different substances and paraffin. Find neutron, proton
