Honors General Chemistry
Honors General Chemistry CHEM 121
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This 1 page Class Notes was uploaded by Dr. Drew Flatley on Friday October 30, 2015. The Class Notes belongs to CHEM 121 at University of Massachusetts taught by Staff in Fall. Since its upload, it has received 13 views. For similar materials see /class/232357/chem-121-university-of-massachusetts in Chemistry at University of Massachusetts.
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Date Created: 10/30/15
CHEM121H Honors General Chemistry 1 Mass Terms and Units Used in Describing Atoms Atomic 0r Proton Number 1Z17 The number of protons in the atomic nucleus Always a whole number This is the basis for element ordering in the periodic table For example Z 1 for H Z 6 for C and Z 109 for Mt Meitnerium Mass or Nucleon Number 1A17 The total number of protons and neutrons collectively called nucleons in the nucleus of the atom The mass number is always a whole number For example the mass number oflOB is 10 5 protons 5 neutrons Atomic Mass 1mg 7 The rest mass of an atom in its electronic and nuclear ground state NonSI unit The most common unit used is the uni ed atomic mass unit amu or u defined as 112 the mass ofa carbon12 atom in its ground state1 u 1661 x 103924 g For example the atomic mass ofa 10B isotope is 1001294 u and the atomic mass ofa 11B isotope is 1100931 u Atomic Weight 0r Relative Atomic Mass A17 The weighted average mass of all naturally occurring isotopes of that element For example boron has two naturally occurring isotopes 10B 199 and 11B 801 The weighted average ofthese is 10799 u Mass Defect 7 The difference between the calculated mass of an atom based on the sum of the rest masses of the subatomic particles making up the atom and its experimentally determined atomic mass The mass defect is converted into binding energy BE upon formation of the atom From Mills 1 et al Quantities units and symbols in physical chemistry The Green Book IUPAC Blackwell Publications Oxford 1988 and McNaught A D Wilkinson A Compendium of chemical terminology 2e The Gold Book IUPAC Blackwell Publications Oxford 1997 D L Adams 952008