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1、STANDARD ATOMIC WEIGHTS (2005)This table of atomic weights includes the changes made in 2005 by the IUPAC Commission on Isotopic Abundances and Atomic Weights . Those changes affected the following elements: Al, Au, Bi, Co, Cs, La, Mn, Na, Nd, P, Pt, Sm, Sc, Ta, Tb, and Th . The Standard Atomic Weig
2、hts apply to the elements as they ex- ist naturally on Earth, and the uncertainties take into account the isotopic variation found in most laboratory samples . Further com- ments on the variability are given in the footnotes . The number in parentheses following the atomic weight value gives the unc
3、ertainty in the last digit . An atomic weight entry in brackets indicates that the element that has no stable isotopes; the value given is the atomic mass in u (or the mass number, if the mass is not accurately known) for the isotope of longest half-life . Thorium, protactinium, and uranium have no
4、stable isotopes, but the terrestrial isotopic composition is sufficiently uniform to per- mit a standard atomic weight to be specified .References1 . Chemistry International, Vol . 27, No . 6, p .18, 2005 .2 . Coplen, T . D ., Pure Appl. Chem . 73, 667, 2001 .3 . Coplen, T . D ., J. Phys. Chem. Ref.
5、 Data, 30, 701, 2001 .NameSymbolAtomic no.Atomic weightFootnotesActiniumAc89227 .0277a AluminumAl1326 .9815386(8) AmericiumAm95243 .0614a AntimonySb51121 .760(1)g ArgonAr1839 .948(1)g r ArsenicAs3374 .92160(2) AstatineAt85209 .9871a BariumBa56137 .327(7) BerkeliumBk97247 .0703a BerylliumBe49 .012182
6、(3) BismuthBi83208 .98040(1) BohriumBh107264 .12a BoronB510 .811(7)g m r BromineBr3579 .904(1) CadmiumCd48112 .411(8)g CalciumCa2040 .078(4)g CaliforniumCf98251 .0796a CarbonC612 .0107(8)g r CeriumCe58140 .116(1)g CesiumCs55132 .9054519(2) ChlorineCl1735 .453(2)g m r ChromiumCr2451 .9961(6) CobaltCo
7、2758 .933195(5) CopperCu2963 .546(3)r CuriumCm96247 .0704a DarmstadtiumDs110271a DubniumDb105262 .1141a DysprosiumDy66162 .500(1)g EinsteiniumEs99252 .0830a ErbiumEr68167 .259(3)g EuropiumEu63151 .964(1)g FermiumFm100257 .0951a FluorineF918 .9984032(5) FranciumFr87223 .0197a GadoliniumGd64157 .25(3)
8、g GalliumGa3169 .723(1) GermaniumGe3272 .64(1) GoldAu79196 .966569(4) HafniumHf72178 .49(2) HassiumHs108277a HeliumHe24 .002602(2)g r HolmiumHo67164 .93032(2) HydrogenH11 .00794(7)g m r IndiumIn49114 .818(3)NameSymbolAtomic no.Atomic weightFootnotesIodineI53126 .90447(3) IridiumIr77192 .217(3) IronF
9、e2655 .845(2) KryptonKr3683 .798(2)g m LanthanumLa57138 .90547(7)g LawrenciumLr103262 .1097a LeadPb82207 .2(1)g r LithiumLi36 .941(2)b g m r LutetiumLu71174 .967(1)g MagnesiumMg1224 .3050(6) ManganeseMn2554 .938045(5) MeitneriumMt109268 .1388a MendeleviumMd101258 .0984a MercuryHg80200 .59(2) Molybde
10、numMo4295 .94(2)g NeodymiumNd60144 .242(3)g NeonNe1020 .1797(6)g m NeptuniumNp93237 .0482a NickelNi2858 .6934(2) NiobiumNb4192 .90638(2) NitrogenN714 .0067(2)g r NobeliumNo102259 .1010a OsmiumOs76190 .23(3)g OxygenO815 .9994(3)g r PalladiumPd46106 .42(1)g PhosphorusP1530 .973762(2) PlatinumPt78195 .
11、084(9) PlutoniumPu94244 .0642a PoloniumPo84208 .9824a PotassiumK1939 .0983(1)g PraseodymiumPr59140 .90765(2) PromethiumPm61144 .9127a ProtactiniumPa91231 .03588(2) RadiumRa88226 .0254a RadonRn86222 .0176a RheniumRe75186 .207(1) RhodiumRh45102 .90550(2) RoentgeniumRg111272 .1535a RubidiumRb3785 .4678
12、(3)g RutheniumRu44101 .07(2)g RutherfordiumRf104261 .1088a SamariumSm62150 .36(2)g ScandiumSc2144 .955912(6) SeaborgiumSg106266 .1219a1-7487_S01.indb 74/10/06 9:33:14 AMNameSymbolAtomic no.Atomic weightFootnotesSeleniumSe3478 .96(3)r SiliconSi1428 .0855(3)r SilverAg47107 .8682(2)g SodiumNa1122 .9897
13、6928(2) StrontiumSr3887 .62(1)g r SulfurS1632 .065(5)g r TantalumTa73180 .94788(2) TechnetiumTc4397 .9072a TelluriumTe52127 .60(3)g TerbiumTb65158 .92535(2) ThalliumTl81204 .3833(2) ThoriumTh90232 .03806(2)g ThuliumTm69168 .93421(2)NameSymbolAtomic no.Atomic weightFootnotesTinSn50118 .710(7)g Titani
14、umTi2247 .867(1) TungstenW74183 .84(1) UnunbiumUub112285a UnunhexiumUuh116289a UnunquadiumUuq114289a UraniumU92238 .02891(3)g m VanadiumV2350 .9415(1) XenonXe54131 .293(6)g m YtterbiumYb70173 .04(3)g YttriumY3988 .90585(2) ZincZn3065 .409(4) ZirconiumZr4091 .224(2)ga No stable isotope exists . The a
15、tomic mass in u (or the mass number, if the mass is not accurately known) is given in brackets for the isotope of longest half-life .b Commercially available Li materials have atomic weights that range between 6 .939 and 6 .996; if a more accurate value is required, it must be determined for the spe
16、cific material . g Geological specimens are known in which the element has an isotopic composition outside the limits for the normal material . The difference between the atomic weight of the element in such specimens and that given in the table may exceed the stated uncertainty . m Modified isotopic compositions may be found in commercially available material because it has been subject to an undisclosed or
