Theatomicweights,Ar(E),ofmanyelementsvaryduetovariationsintheabundancesoftheirisotopesinnaturalterrestrialmaterials.For10oftheseelements,anatomic-weightintervalisgivenwiththesymbol[a;b]todenotethesetofatomic-weightvaluesinnormalmaterials;thus,a≤Ar(E)≤bforelementE.Thesymbolsaandbdenotetheboundsoftheinterval[a;b].Figuresinthisreportdisplaydistributionsofatomic-weightvariationforspecifiedelements.IfamoreaccurateAr(E)valueisrequired,itmustbedeterminedforthespecificmaterial.For74elements,Ar(E)valuesandtheirdecisionaluncertainties(inparentheses,followingthelastsignificantfiguretowhichtheyareattributed)aregiven.ThefootnotestothistableelaboratethetypesofvariationthatmayoccurforindividualelementsandthatmaybelargerthanthelisteduncertaintiesofvaluesofAr(E)ormaylieoutsidethevalueslisted.Namesofelementswithatomicnumber113to118areprovisional;theyhavebeenreportedinthepeer-reviewed,scientificliterature,buttheyhavenotyetbeennamedbyIUPAC.2009年国际标准相对原子质量NumberNameSymbolAtomicWeightFootnotes1hydrogen氢H[1.00784;1.00811]m2helium氦He4.002602(2)gr3lithium锂Li[6.938;6.997]m4beryllium铍Be9.012182(3)​5boron硼B[10.806;10.821]m6carbon碳C[12.0096;12.0116]​7nitrogen氮N[14.00643;14.00728]​8oxygen氧O[15.99903;15.99977]​9fluorine氟F18.9984032(5)​10neon氖Ne20.1797(6)gm11sodium钠Na22.98976928(2)​12magnesium镁Mg24.3050(6)​13aluminium(aluminum)铝Al26.9815386(8)​14silicon硅Si[28.084;28.086]​15phosphorus磷P30.973762(2)​16sulfur硫S[32.059;32.076]​17chlorine氯Cl[35.446;35.457]m18argon氩Ar39.948(1)gr19potassium钾K39.0983(1)​20calcium钙Ca40.078(4)g21scandium钪Sc44.955912(6)​22titanium钛Ti47.867(1)​23vanadium钒V50.9415(1)​24chromium铬Cr51.9961(6)​25manganese锰Mn54.938045(5)​26iron铁Fe55.845(2)​27cobalt钴Co58.933195(5)​28nickel镍Ni58.6934(4)r29copper铜Cu63.546(3)r30zinc锌Zn65.38(2)r31gallium镓Ga69.723(1)​32germanium锗Ge72.63(1)​33arsenic砷As74.92160(2)​34selenium硒Se78.96(3)r35bromine溴Br79.904(1)​36krypton氪Kr83.798(2)gm37rubidium铷Rb85.4678(3)g38strontium锶Sr87.62(1)gr39yttrium钇Y88.90585(2)​40zirconium锆Zr91.224(2)g41niobium铌Nb92.90638(2)​42molybdenum钼Mo95.96(2)g43technetium*锝Tc​​44ruthenium钌Ru101.07(2)g45rhodium铑Rh102.90550(2)​46palladium钯Pd106.42(1)g47silver银Ag107.8682(2)g48cadmium镉Cd112.411(8)g49indium铟In114.818(3)​50tin锡Sn118.710(7)g51antimony锑Sb121.760(1)g52tellurium碲Te127.60(3)g53iodine碘I126.90447(3)​54xenon氙Xe131.293(6)gm55caesium(Cesium)铯Cs132.9054519(2)​56barium钡Ba137.327(7)​57lanthanum镧La138.90547(7)g58cerium铈Ce140.116(1)g59praseodymium镨Pr140.90765(2)​60neodymium钕Nd144.242(3)g61promethium*钷Pm​​62samarium钐Sm150.36(2)g63europium铕Eu151.964(1)g64gadolinium钆Gd157.25(3)g65terbium铽Tb158.92535(2)​66dysprosium镝Dy162.500(1)g67holmium钬Ho164.93032(2)​68erbium铒Er167.259(3)g69thulium铥Tm168.93421(2)​70ytterbium镱Yb173.054(5)g71lutetium镥Lu174.9668(1)g72hafnium铪Hf178.49(2)​73tantalum钽Ta180.94788(2)​74tungsten钨W183.84(1)​75rhenium铼Re186.207(1)​76osmium锇Os190.23(3)g77iridium铱Ir192.217(3)​78platinum铂Pt195.084(9)​79gold金Au196.966569(4)​80mercury汞Hg200.59(2)​81thallium铊Tl[204.382;204.385]​82lead铅Pb207.2(1)gr83bismuth铋Bi208.98040(1)​84polonium*钋Po​​85astatine*砹At​​86radon*氡Rn​​87francium*钫Fr​​88radium*镭Ra​​89actinium*锕Ac​​90thorium*钍Th232.03806(2)g91protactinium*镤Pa231.03588(2)​92uranium*铀U238.02891(3)gm93neptunium*镎Np​​94plutonium*钚Pu​​95americium*镅Am​​96curium*锔Cm​​97berkelium*锫Bk​​98californium*锎Cf​​99einsteinium*锿Es​​100fermium*镄Fm​​101mendelevium*钔Md​​102nobelium*锘No​​103lawrencium*铹Lr​​104rutherfordium*Rf​​105dubnium*Db​​106seaborgium*Sg​​107bohrium*Bh​​108hassium*Hs​​109meitnerium*Mt​​110darmstadtium*Ds​​111roentgenium*Rg​​112copernicium*Cn​​113ununtrium*Uut​​114ununquadium*Uuq​​115ununpentium*Uup​​116ununhexium*Uuh​​118ununoctium*Uuo​​以下是翻译为中文的上表附注：*这些是没有稳定同位素的元素.一个或多个已知同位素已列在“参考资料”中的“Table3”中，并给出了合适的相对原子质量和半衰期。