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460 BCE
Democritus
-440's B.C, contributed to astronomy that the atomic theory, the belief that everything in the world consists of particles called atoms
-Atomic theory stated “The universe is composed of two elements: the atoms & the void in which they exist/move.”
-Hypothesised that atoms can't be destroyed, differ in size/shape/temperature, always moving, & invisible. Believed there were infinite number of atoms. This was created in 465BC
-His atomic model was made in 400BC
-Discovered atom during Greek Era -
John Dalton
-first useful atomic theory of matter, 1803
-Concluded that evaporated water exists in air as an independent gas, early 1800
-Developed the hypothesis that sizes of the particles making up different gases must be different, 1803
-Introduced concepts on the modern periodic table in 1803
-was first to talk about color blindness & explain it
-1803 revealed the concept of Dalton’s Law of Partial Pressures.
-1800s, the 1st to explain the behavior of atoms
-Daltons model was made in 1803 -
J.J. Thompson
-1890's he discovered that the particles that made up the gases were universal.
-He used things like vacuums, Rays, and the way things deflected to get his discovery (1890's)
-Determined that all matter is made up of tiny particles that are much smaller than atoms (1890's)
-1912, discovered that neon was composed of two different types of atoms, which proved the existence of of isotopes in a stable element.
-Plum pudding model made in 1904 -
Ernest Rutherford
-1895 he discovered an easier way to detect radio waves
-Early 1900's him and another person went on to categorize radioactive elements into what they called "decay series".
-Credited with discovering the radioactive gas radon while at McGill
-1907, discovered that nearly the total mass of an atom is concentrated in a nucleus
-In 1907 he made the nuclear model
-1919, he discovered how to artificially induce a nuclear reaction in a stable element.
-Rutherford model made in 1911 -
Niels Bohr
-Early 1900's, he theorized In a series of articles that atoms give off electromagnetic radiation as a result of electrons jumping to different orbit levels
-Late 1930's, he contributed in the liquid droplet theory
-Established the CERN in 1954
-More than 100 publications to his name
-1939, started to help make an atomic bomb
-He made the Bohr model in 1913
