Geological specimens are known in which the element has an isotopic composition outside the limits for normal material.See original paper for the range of these elements from different sources List of Elements with Range of Atomic Weights. See also a copy of the periodic table with atomic weights to five significant figures. See below for the elements listed in Atomic Number Order or Name order. The original paper should be consulted for full details of the variation in atomic weight and the half life of the radioisotopes quoted below.Ī number in parentheses indicates the uncertainty in the last digit of the atomic weight. For radioactive elements the isotope with the longest half-life is quoted in parenthesis. In the other lists the values quoted are those suggested for material where the origin of the sample is unknown. The standard atomic weights of twelve elements having two or more stable isotopes have variability of atomic-weight values in natural terrestrial materials. Previous values may be consulted from the 1993 table, the 1995 table, the 1997 table, the 1999 table, the 2001 table, the 2005 table, the 2007 table, the 2009 table, the 2011 table, the 2013 table, the 2015 table or the 2019 table. World Wide Web version of atomic weight data originally prepared by G. These tables are based on the 2021 table with changes from the 2019 table for the values of Ar, Hf, Ir, Pb and Yb and changes to the uncertainty for Al, Au, Co, F, Ho, Mn, Nb, Pa, Pr, Rh, Sc, Tb, Tm, and Y. a pollution of 1 gram of benzene in a certain amount of water converts to N A/78.11≈ 7.2021 Atomic Weights IUPAC Commission on Isotopic Abundances and Atomic Weights. Using the above calculator you could find that e.g. Or 1 mole of a substance will contain Avogadro's number of that substance. The term " mole" is defined in that one mole of a substance with a molecular (or atomic) mass of one (1), will have a mass of 1 gram. It is defined to be 1/12 of the mass of one atom of carbon-12 and in older works is also abbreviated as "amu".Īlso, important in this field is Avogadro's number (N A) or Avogadro's constant (6.0221 x 10 23). In related terms, another unit of mass often used is Dalton (Da) or unified atomic mass unit (u) when describing atomic masses and molecular masses. Molecular mass or molar mass are used in stoichiometry calculations in chemistry. This Calculator has been tested on Internet Explorer version 6 only,įirefox might not show all fields correctly. For question or remarks please contact us. !!! Lenntech BV cannot be held responsible for errors in the calculation, Make sure you enter the molecule of crystallization at last (e.g. The calculator handles at most two different bracket levels. The molecular mass calculator will recognize the entered formula's, which are included in the list of organic compounds. Or you can choose by one of the next two option-lists, which contains a series of common organic compounds (including their chemical formula) and all the elements. This online calculator you can use for computing the average molecular weight (MW) of molecules by entering the chemical formulas (for example C3H4OH(COOH)3 ). Molecular Weight Calculator Molecular Weight Calculator Separation and Concentration Purification Request.Plant Inspection & Process Optimalisation.