Atomic Weights of the Elements 1995

The biennial review of atomic weight, $A_r$ (E), determinations and other cognate data has resulted in changes for the standard atomic weight of 21 elements. The five most significant changes are: boron from $\text{10.811±0.005}$ to $\text{10.811±0.007;}$ carbon from $\text{12.011±0.001}$ to $\text{12.0107±0.0008;}$ arsenic from $\text{74.92159±0.00002}$ to $\text{74.92160±0.00002;}$ cerium from $\text{140.115±0.004}$ to $\text{140.116±0.001;}$ and platinum $\text{195.08±0.03}$ to $\text{195.078±0.002.}$ An annotation for potassium has been changed in the Table of Standard Atomic Weights. To eliminate possible confusion in the reporting of relative lithium isotope-ratio data, the Commission recommends that such data be expressed using ${}^7{\mathrm{Li/}}^{\mathrm{6}}\mathrm{Li}$ ratios and that reporting using ${}^6{\mathrm{Li/}}^{\mathrm{7}}\mathrm{Li}$ ratios be discontinued. Because relative isotope-ratio data for sulfur are commonly being expressed on noncorresponding scales, the Commission recommends that such isotopic data be expressed relative to VCDT (Vienna Cañon Diablo Troilite) on a scale such that ${}^{34}{\mathrm{S/}}^{\mathrm{32}}\mathrm{S}$ of IAEA-S-1 silver sulfide is 0.9997 times that of VCDT. Many elements have a different isotopic composition in some nonterrestrial materials. Some recent data on oxygen are included in this article for the information of the interested scientific community.