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460
Democritus 460 B.C. - 370 B.C.
He believed that all matter consisted of extremely small particles that could not be divided. He theorized that empty space lie in an atom helping matter to be split infinitley -
Joseph Proust 1724-1826
Created the law of definite proportions. This is when chemical substances only truly combine to form a small number of compounds, each of which is characterized by components that combine in fixed proportions by weight. His beliefs were not at first accepted but later on were. -
Antoine Lavoisier 1743-1794
He stated the first version of the law of conservation of mass, recognized and named oxygen, and hydrogen, he abolished the phlogiston theory and helped construct the metric system, he wrote the first extensive list of elements, and helped to reform chemical nomenclature, and he discovered that although matter may change its form or shape, its mass always remains the same. -
John Dalton 1766 - 1844
Dalton proposed the theory that all matter is madde of individual particles called atoms, which cannot be divided. He used a soliid wooden model of spheres to help prove his theory. All had different masses. -
J.J Thomson 1856 - 1940
He used an electric current to learn morer about atoms. To do this, he used aa sealed tube of gas / he saw that when the current is turned on, one disk becomes negatively charged and the other is positively charged causing a glowing beam to apper in the tube -
Hantaro Nagaoka 1865-1950
He suggested that an atom has a central nucleus because electrons move in orbits like the rings of saturn. -
Robert Milikan 1868-1953
He worked on an oil-drop experiment in which they measured the charge on a single electron. His experiment measured the force on tiny charged droplets of oil suspended against gravity between two metal electrodes. -
Ernest Rutherford 1871-1937
He discovered that uranium emits fast moving particles that have a positive charge. Rutherford hypothesized that the mass and charge at any location in the gold would be too small to change the path of an alpha particle based on Thomson's model of the atom. -
Neils Bohr 1885-1962
He created a model of atoms that forced on electrons such as thier arrangement in an atom and that electrons travel in discrete (detachted or individual) orbit around the atoms nucleus. He looked at similar stuctures of the solar system. This was an improvement on the earlier cubic model, plum-pudding model, Saturnian model, and the Rutherford model. -
Erwin Shrodinger 1887-1961
He developed mathmatical equations to describe the motion of electrons in atoms. His work lead to the electron cloud model. -
Ernest Marsden 1889-1970
Found out what happens to alpha particles when they pass through a thin sheet of gold. -
James Chadwick 1891-1974
Chadwick confirmed the existance of nuetrons which have no change. Atomic nucleus contain nuetrons and positiveley charged protons. -
Louis de Broglie 1892-1987
He proposed that moving particles like electrons have some properties of waves. He collected evidence to support that. -
Aristotle 384 B.C. - 322 B.C.
Aristotle did not think there was a limit to the number of times matter could be divided. He used a model using the 4 elements and the 4 combinations
-Air, Fire, Earth, and Water
-Wet, Hot, Dry, and Cold
