Atomic weights of the elements 1999

The biennial review of atomic-weight, A(r)(E), determinations and other cog nate data have resulted in changes for the standard atomic weights of the f ollowing elements. [GRAPHICS] Presented are updated tables of the standard atomic weights and their uncer tainties estimated by combining experimental uncertainties and terrestrial variabilities. In addition, this report again contains an updated table of relative atomic-mass values and half-lives of selected radioisotopes. Chang es in the evaluated isotopic abundance values from those published in 1997 are so minor that an updated list will not be published for the year 1999. Many elements have a different isotopic composition in some nonterrestrial materials. Some recent data on parent nuclides that might affect isotopic a bundances or atomic-weight values are included in this report for the infor mation of the interested scientific community.