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400 BCE
Democritus
Introduced the idea that an atom is the basic building block for everything. -
399 BCE
Hsiung Nu-(Huns) Dominate Mongolia
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John Dalton “marble” model
All matter was composed of invisible and indestructible atoms with distinct masses and properties -
Period: to
Russo Persian War
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Michael Faraday
Introduced the idea that atoms could interact through forces of electricity and magnetism. -
Eugen Goldstein
Discovered canal rays(+charged particles) contributing to the understanding that atoms contain subatomic particles. -
JJ Thomson “plum pudding” Model
Discovered the electron, proposed the “plum pudding/chocolate chip cookie” model where electrons are embedded in a positively charged sphere, introducing the concept of interval structure in atoms. -
Slavery Banned in Brazil
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Ernest Rutherford “Nuclear” Model/“Jimmy Neutron” Model
Discovered the nucleus, created the “nuclear” model with a dense positively charged core and electrons orbiting it. -
Robert Millikan
Used the oil drop experiment to discover the charge of a single electron. -
Neils Bohr “Solar system” model
Proposed a model of the atom in which electrons orbit the nucleus in a planetary-like style. -
Period: to
World War 1
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Werner Heisenberg
Werner Heisenberg contributed to atomic theory by establishing the uncertainty principle, which specifies that a particle's location and momentum cannot be precisely determined, and formulating quantum mechanics in terms of matrices. -
Edwin Schrödinger “Electron Cloud” Model
Stated that electrons could not be pinpointed, but used equations to find an area where they would likely be. -
Stock Market Crash/Great Depression
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James Chadwick “Electron Cloud” Model with Neutrons Added
The neutron was discovered as a result of James Chadwick's Atomic Theory. In it, he fired high-energy particles at a beryllium sheet. Other particles, including the atom's neutron, were discharged. -
Franklin D. Roosevelt Elected