n. (Chem.) A metallic element separated from ytterbium in 1907, by Urbain in Paris and by von Welsbach in Vienna. It is a member of the Lanthanide rare earth group. Symbol, Lu; atomic number 71; atomic weight 174.967 [ C=12.011 ]. Previously spelled Lutecium. [ Webster 1913 Suppl. +PJC ]