any of a group of 17 chemically similar metallic elements, including scandium, yttrium, and the lanthanides

Any of the six chemical elements in group 2 of the periodic table, including [[铍|鈹|pi2]], [[镁|鎂|mei3]], [[钙|鈣|gai4]], [[锶|鍶|si1]], [[钡|鋇|bei4]], and [[镭|鐳|lei2]]