17 in all. July 4, 2012 Zayne Turner Cerium. Dysprosium. Erbium. Europium. Gadolinium. Holmium. Lanthanum. Lutetium. ↓ Neodymium. Praseodymium. Samarium. Scandium. Terbium. Thulium. Ytterbium. Yttrium. Oh. And Shelly's favorite, Promethium. [cf. Bayan Obo.] *image courtesy Lettre Sauvage.