IUPAC atomic weights

Atomic number 30, atomic relative mass 65.39 (a value of 65.409 is recommended by the IUPAC Atomic Weights Commission, 2005). 

Commision on Atomic Weights, Inorganic Chemistry Division of IUPAC, Atomic weights of the elements 1975, Pure Appl. Chem. 1976, 47, 75-95. 

Atoms of the same element (having the same atomic number) but differing in atomic weight. The isotopes of an element all have the same chemical properties. See Radioactive Isotopes. IUPAC... 

Atomic weight of Cd, AW g mol 1 (SI units)3 7 x 10-5 Statement by IUPAC describing measurement of the atomic weight and assignment of uncertainty... 

IUPAC (1984) Element by element review of their atomic weights. Pure Appl Chem, IUPAC 56 741-742... 

Atomic weight values. These are fundamental constants available from IUPAC tables... 

IUPAC Commission on Atomic Weights and Isotopic Abundances. Pure Appl. Chem. 1994, <56, 2423. 

E-mail Address secretariat iupac.org Web Address www.iupac.org The International Union of Pure and Applied Chemistry (IUPAC) is a world authority on chemical nomenclature, terminology, standardized methods for measurement, atomic weights and other critically evaluated data. 

The atomic weights used in computing formula weights and volumetric and gravimetric factors stated in tests and assays are those recommended in 1991 by the IUPAC Commission on Isotopic Abundances and Atomic Weights. 

For molecules Mr is the relative molecular mass or molecular weight for atoms Mr is the relative atomic mass or atomic weight and the symbol Ar may be used. Mr may also be called the relative molar mass, Mr>B = Mb/M, where M = 1 gmol-. The standard atomic weights, recommended by IUPAC, are listed in table 6.2, p.94. 

As agreed by the IUPAC Commission on Atomic Weights and Isotopic Abundances in 1979 [42] the relative atomic mass (atomic weight) of an element, E, can be defined for any specified sample. It is the average mass of its atoms in the sample divided by the unified atomic mass unit1 or alternatively the molar mass of its atoms divided by the standard molar mass M = Lmu = 1 gmol-1 ... 

The variations in isotopic composition of many elements in samples of different origin limit the precision to which a relative atomic mass can be given. The standard atomic weights revised biennially by the IUPAC Commission on Atomic Weights and Isotopic Abundances are meant to be applicable for normal materials. This means that to a high level of confidence the relative atomic mass of an element in any normal sample will be within the uncertainty limits of the tabulated value. By normal it is meant here that the material is a reasonably possible source of the element or its compounds in commerce for industry and science and that it has not been subject to significant modification of isotopic composition within a geologically brief period [43]. This, of course, excludes materials studied themselves for very anomalous isotopic composition. 

Table 6.2 lists the relative atomic masses of the elements in the alphabetical order of chemical symbols. The values have been recommended by the IUPAC Commission on Atomic Weights and Isotopic Abundances in 1991 [44] and apply to elements as they exist naturally on earth. 

CoPLEN TB (2001) Atomic Weights of the Elements 1999 (IUPAC Technical Report). PureAppl Chem 78 667-683. 

Many of the isotope masses have been determined by MS accurately to seven or more decimal places. Numbers in parentheses in the atomic weights represent the first uncertain figure. Atomic weights based on the values in Pure Appl.Chem. 2001, 73, 667-683 as tabulated at http //www.chem.qmul.ac.uk/iupac/AtWt/. Used with permission. 

Source Data from Atomic Weights of the Elements 2009, lUPAC. See iupac.org/pubUcations/pac/83/2/0359/ Values in parentheses are mass numbers of the longest-lived known isotopes. 

Values from the 2001 table Pure Appl. Chem., 2003, 75 1107-1122. The values of zinc, krypton, molybdenum, and dysprosium have been modified. The approved name for element 110 is included see Pure Appl. Chem., 2003, 75 1613-1615. The proposed name for element 111 is also included. Reproduced from http //www.chem.qmul.ac.uk/iupac/AtWt/. The table is also available from mirror sites in Germany, Japan, South Africa, and USA. World Wide Web version of atomic weight data prepared by G. P. Moss, originally from a file provided by D. R. Tide. Note The claim [Phys. Rev. Lett., 1999, 83 1104) for elements 116 and 118 has been withdrawn (see Chem. Eng. News, 2001, 79 10 (6 August 2001) 2002, 80 12 (22 July 2002) Phys. Rev. Lett., 2002, 89 039901). Previous values may be consulted from the 1993 table, the 1995 table, the 1997 table or the 1999 table. The original paper should be consulted for details of the half-life of the radioisotopes quoted below. Also there is a report on the different isotopic compositions of some non-terrestrial materials. A number in parentheses indicates the uncertainty in the last digit of the atomic weight. 

The atomic weights for these elements and a few others are now given as tenges due to the variability of values In natural terrestrial materials. (Atomic weights are based on the 2009 values in Pure Appl. Chem., 2011,83, 359-396 as tabulated at http ///www.ohem.qmul.ac.uk/iupac/AtWt/.) With permission. Newer tables now provide a range of Isotope abundances of some elements due to variations in Earthly sources. Other celestial bodies (e.g., Moon, Mars, asteroidal meteorites) display even more different Isotope variations, which enables MS measurements to identify the particular source of some meteorites. 

Coplen, T.B. (2008) Explanatory Glossary of Terms Used in Expression of Relative Isotope Ratios and Gas Ratios, International Union of Pure and Applied Chemistry Inorganic Chemistry Division, Commission on Isotopic Abundances and Atomic Weights, Peer Review, January 16, 2008, http //www.iupac.org (accessed 14 May 2014). 

Descriptive properties for a basic group of approximately 1400 inorganic compounds are compiled in Section 3. These follow a concise, revised introduction to inorganic nomenclature that follows the recommendations of the IUPAC published in 1990. In this section are given the exact atomic (or formula) weight of the elements accompanied, when available, by the uncertainty in the final figure given in parentheses. 

The molecular weight of a polymer is of prime importance in the polymer s synthesis and application. Chemists usually use the term molecular weight to describe the size of a molecule. The more accurate term is molar mass, usually in units of g mol-1. The term molecular weight is the ratio of the average mass per formula unit of a substance to - th of the mass of an atom of 12C and is dimensionless (IUPAC, 1991, in press). This text will use molecular weight throughout irrespective of the units, because molecular weight is the more familiar term for most chemists. 

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