Pure and Applied Chemistry

The biennial review of atomic-weight, A_r(E), determinations and other cognate data have resulted in changes for the standard atomic weights of the following elements:

	From	To
Zinc	65.39 ± 0.02	65.409 ± 0.004
Krypton	83.80 ± 0.01	83.798 ± 0.002
Molybdenum	95.94 ± 0.01	95.94 ± 0.02
Dysprosium	162.50 ± 0.03	162.500 ± 0.001

Presented are updated tables of the standard atomic weights and their uncertainties estimated by combining experimental uncertainties and terrestrial variabilities. In addition, this report again contains an updated table of relative atomicmass values and half-lives of selected radioisotopes. Changes in the evaluated isotope abundance values from those published in 1997 are relatively minor and will be published in a major review of each element in 2003. Many elements have a different isotopic composition in some nonterrestrial materials. Some recent data on parent nuclides that might affect isotope abundances or atomic-weight values are included in this report for the information of the interested scientific community.