Gadolinium, lutetium and zirconium all have new atomic weights

The International Union of Pure and Applied Chemistry (Iupac) has updated the standard atomic weights of gadolinium, lutetium and zirconium following a detailed review of their isotopic abundances.

Gadolinium’s standard atomic weight was revised from 157.250 to 157.249. Similarly, lutetium’s weight changed from 174.9668 to 174.96669, while zirconium’s was updated from 91.224 to 91.222. The revisions follow a review by Iupac’s commission on isotopic abundances and atomic weights, who noted that gadolinium’s standard atomic weight had remained unchanged since 1969, based on isotopic data from the 1940s. Recent evaluations of their natural isotopic abundances prompted this update. For lutetium and zirconium, more accurate measurements of their isotopic compositions have been obtained since their weights were last updated in 2007 and 1983, respectively.