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15 Cards in this Set

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  • Back
400 B.C.; the world is composed of 2 things: 1. atoms 2. empty space
Dalton's Atomic Theory
1.All atoms are composed of tiny particles called atoms
2.Atoms of the same elements are identical to each other and atoms of different elements are different
3.Atoms of different elements can mix together or chemically combine with each other in whole number ratio to form compounds
4.Chemical reactions occur when atoms are seperated, joined or rearranged (atoms of one element cannot change into another)
negatively charged subatomic particles (J. J. Thompson)
Cathode Ray
a stream of electrons produced at the negative electrode (cathode) of a tube containing a gas at low pressure
negatively charged
positively charged
Robert A. Milikin
discovered the quanity charge carried by an electron
postively charged subatomic particles (Goldstein)
subatomic particles with no charge but with a mass nearly equal to that of a proton (Chadwick)
Gold Foil Experiment
Atomic Number
is the number of protons in the nucleus of an atom of that element
Mass Number
total number of protons and neutrons in an atom
How can you find the number of neutrons?
# of neutrons=
mass # - atomic #
atoms of the same element that have the same atomic number but different atomic masses due to a different number of neutrons
Atomic Mass
a weighted average mass of the atoms in a naturally occuring sample of the element