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Unformatted text preview: 9/4/08 masses of atoms need a unit to measure mass get masses! Mass of proton=10^-24 g---1 atomic mass unit=u one atom of 12 C has mass 12u what is the mass of carbon-12? 6Xmass of proton+6xmass neutron+6xmass of e- you can't find the mass this wayEinstein was first to relate mass and energy. Mass spectrometer(fig, 2-14): measures atomic mass as ratio counting atoms-Avogadro's #= N A . The # of 12 C atoms in 12 g of 12 C-measured quantity 6.022 x 10 23--- 1 mol of object is N A objects. Molar masses-mass of 1 mol 12c=12 g molar mass is really 12.011 g- takes into account all the isotopes. Read chap 3.1-3.3 and look over 3.4-3.6 (nomenclature) Molecules-atoms held in molecules by chemical bonds. Covalent-shared electrons, ionic-transfer of 1 or more electrons-charged atoms covalent- single H H double O=C=O triple N ionic-NaCl--- Na + Cl- , formula unit representing a molecule empirical formula- relative #'s of atoms...
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