atomic theory of matter - developed by John Dalton
- all elements are composed of atoms
- atoms in each element are identical
- chemical reactions can't change, create, or destroy atoms
- compounds are combinations of atoms
- atoms - smallest particles of an element that still contain all the characteristics of that element
- law of constant composition - kinds of atoms and their ratios are constant in compounds
- law of conservation of mass - total mass after a reaction is equal to total mass before the reaction
- law of multiple proportions - atoms combine in compounds in simple ratios
cathode ray tubes - vacuum tube through which high voltage creates radiation
- produce rays that cause glass to fluoresce, give off light
- electrons move from the cathode (-) to the anode (+)
- J. J. Thomson - summarized his cathode ray observations and found the electron's electrical charge to be 1.76 x 108 coulombs per gram
- Robert Millikan - used his "oil-drop" experiment to calculate the mass of the electron by using his measurements of the charge in a single electron and Thomson's calculations
radioactivity - spontaneous emission of radiation
- Ernest Rutherford - aka "the second Newton"; discovered the 3 types of radiation
- alpha radiation - positive charge, more massive than beta; equal to nuclei of helium
- beta radiation - negative charge, less massive than alpha; equal to high speed electrons/cathode rays
- gamma radiation - unaffected by electrical fields, has no charge
nuclear atom - final view of atom discovered by Rutherford
- J. J. Thomson - believed that electrons were embedded in a positively charged sphere
- Ernest Rutherford - used gold foil experiment to prove that positive charge resided in a very small, dense region called the nucleus
- protons discovered by Rutherford in 1919
- neutrons discovered by James Chadwick in 1932
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