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Atomic Structure

TermDefinition
Democritus proposed that all matter is made up of atoms (tiny, invisible particles); named the atom
Antoine Lavoiser proposed the Law of Conservation of Mass
Law of Conservation of Mass mass is neither created or destroyed during ordinary chemical reactions or physical changes
Joseph Proust proposed the Law of Definite Proportions
Law of Definite Proportions a chemical compound contains the same elements in exactly the same proportions by mass
John Dalton proposed the Law of Multiple Proportions; proposed the Atomic Theory of Matter
Law of Multiple Proportions when two elements A & B form two or more different compounds, the masses of element B, that combined with a fixed mass of element A, can be expressed as a ratio of small whole numbers
Dalton's Atomic Theory -all matter composed of atoms -atoms of a given element are identical in mass & properties -atoms can't be divided, created, or destroyed -atoms of different elements combine in whole number ratios -atoms can be separated, rearranged, or combined
Modern Atomic Theory same as Dalton's except: - not all atoms are identical in mass - atoms can be divided
J.J. Thomson discovered electrons; proposed the plum-pudding model; used a cathode ray
Robert Millikan oil drop experiment; determined the mass of an electron
Henri Becquerel discovered radioactivity
Ernest Rutherford gold foil experiment; discovered atoms have a positive nucleus
Niels Bohr Bohr's model; proposed that electrons travel in fixed orbits around the nucleus
Henry Moseley named the proton; atomic number defines the element
James Chadwick discovered neutrons
Created by: ecornwell
 

 



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