The element with atomic number 71 named after the ancient Roman name for Paris is lutetium. Its symbol is Lu, and it is the final element in the lanthanide series.
The name comes from Lutetia, the Latin name used for Paris in Roman times. French chemist Georges Urbain proposed the name in 1906, initially spelling it “lutecium.” The spelling was later changed to “lutetium” in 1949. Urbain’s naming claim became part of a wider dispute over who had priority in identifying element 71.
Lutetium was found mixed with ytterbium rather than as an easily isolated substance. Urbain, Carl Auer von Welsbach, and Charles James independently worked on separating it, and the discovery story remained controversial for years. The official priority was eventually awarded to Urbain.
Lutetium is a silvery-white, corrosion-resistant metal and one of the heaviest lanthanides. Its radioactive isotope lutetium-177 is important in nuclear medicine, where targeted treatments can deliver radiation to certain tumours. Lutetium-176, with its extremely long half-life, is also useful in dating minerals and meteorites.