-Sm- is a chemical element with atomic number 62. Samarium is a moderately hard silvery metal which readily oxidizes in air. Being a typical member of the lanthanide series, samarium usually assumes the oxidation state +3. Compounds of samarium are also known-- most notably monoxide, monochalcogenides and samarium iodide; samarium iodide is a common reducing agent in chemical synthesis. Samarium has no significant biological role and is only slightly toxic. Although classified as a rare earth element, samarium is the 40th most abundant element in the Earth's crust and is more common than such metals as tin.