Lutetium

Lutetium (IPA: /l(j)uːˈtiːʃiəm/) is a chemical element with the symbol Lu and atomic number 71. A metallic element, lutetium usually occurs in association with yttrium and is sometimes used in metal alloys and as a catalyst in various processes. A strict correlation between periodic table blocks and chemical series for neutral atoms would describe lutetium as a transition metal because it is in the d-block, but it is a lanthanide according to IUPAC.