law of conservation of mass : The amount of stuff after a chemical reaction
takes place is the same as the amount of stuff you started with.
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Le Chatlier's Principle : When you disturb an equilibrium (by adding more
chemical, by heating it up, etc.), it will eventually go back into equilibrium
under a different set of conditions.
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Lewis acid : An electron-pair acceptor (carbonyl groups are really good ones)
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Lewis base : An electron-pair donor. Things with lone pairs like water and
ammonia are really good ones.
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Lewis structure : A structural formula that shows all of the atoms and valence
electrons in a molecule.
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ligand : A molecule or ion that sticks to the central atom in a complex.
Common examples are ammonia, carbon monoxide, or water.
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limiting reagent : If you do a chemical reaction and one of the chemicals gets
used up before the other one, the one that got used up is called the "limiting
reagent" because it limited the amount of product that could be formed. The
other one is called the excess reagent.
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line spectrum : A spectrum showing only certain wavelengths.
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London dispersion force : The forces between nonpolar atoms or molecules
which is caused by momentary induced dipoles. It's real weak.
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lone pair : two electrons that aren't involved in chemical bonding. Also
frequently referred to as an "unshared pair".
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main-block elements : Groups 1,2, and 13-18 in the periodic table. They're
called main block elements because the outermost electron is in the s- or p-
orbitals. What that has to do with the term "main block" is unclear to me, but
hey, that's life.
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mass defect : The difference between the mass of an atom and the sum of
the masses of its individual components. Atoms usually weigh a little less than
if you added up the weights of all the particles. This is because that extra
mass was converted into the energy which holds the atom together (see
"binding energy")
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