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300
Democritus
Defines the atom as an indivisible particle and describes that there are infinite amounts -
Issac Newton
Proposed a mechanical universe with small solid masses in motion. -
Couloumb
formulated the Coulomb's law, which states that that the force between two electrical charges is proportional to the product of the charges and inversely proportional to the square of the distance between them, one of the main forces involved in atomic reactions. -
Dalton
Ceates solid sphere model. Explains a lot of chemical properties such as how atoms combine to form molecules -
John Dalton
Published first atomic theory -
Michael Faraday
Studied the effect of electricity on solutions, coined term "electrolysis" as a splitting of molecules with electricity, developed laws of electrolysis. Faraday himself was not a proponent of atomism. -
J.J Thomson
Created Raisin bun Model which infers on the existence of electrons and protons and presents the idea of a nucleus -
Crookes
created the Crookes’ tube and demonstrated that cathode rays travel in straight lines and produce phosphorescence and heat when they strike certain materials. -
Marie Sklodowska Curie
Studied uranium and thorium and called their spontaneous decay process "radioactivity". She and her husband Pierre also discovered the radioactive elements polonium and radium. -
Nagaoka
Postulated a "Saturnian" model of the atom with flat rings of electrons revolving around a positively charged particle. -
Rutherford
conducted an experiment that led to the understanding of an atom by bombarding gold foil with particles from a radioactive source. his experiment ultimately led to the understanding of the atom -
Robert Millikan
found out the electric charge of the electron -
Robert Millikan
Measured the charge on an electron with the apparatus -
Neils Bohr
stated that the electrons moved around the nucleus in successively large orbits. He also presented the Bohr atomic model which stated that atoms absorb or emit radiation only when the electrons abruptly jump between allowed, or stationary, states. -
H.G.J. Moseley
Using x-ray tubes, determined the charges on the nuclei of most atoms. He wrote"The atomic number of an element is equal to the number of protons in the nucleus". This work was used to reorganize the periodic table based upon atomic number instead of atomic mass. -
Heisenberg
Described atoms by means of formula connected to the frequencies of spectral lines. Proposed Principle of Indeterminancy - you can not know both the position and velocity of a particle. -
Chadwick
discovered the neutrally-charged neutron. -
Otto Hahn
discovered nuclear fission, in which the nucleus of an atom breaks up into two separate nuclei, while experimenting with uranium -
Enrico Fermi
Conducted the first controlled chain reaction releasing energy from the atoms nucleus. -
Murray Gell-Mann and George Zweig
brought forth the idea of "quarks", little bits of matter which when used kind of like building blocks, serve to explain some complex chemical substances. -
JJ Thomson
discovered electrons. began studying positively charged ions. He discovered that neon was composed of two different kinds of atoms, and proved the existence of isotopes in a stable element