| carbon | (n) an abundant nonmetallic tetravalent element occurring in three allotropic forms: amorphous carbon and graphite and diamond; occurs in all organic compounds, Syn. atomic number 6, C |
| dysprosium | (n) a trivalent metallic element of the rare earth group; forms compounds that are highly magnetic, Syn. atomic number 66, Dy |
| erbium | (n) a trivalent metallic element of the rare earth group; occurs with yttrium, Syn. atomic number 68, Er |
| europium | (n) a bivalent and trivalent metallic element of the rare earth group, Syn. atomic number 63, Eu |
| gadolinium | (n) a ductile silvery-white ductile ferromagnetic trivalent metallic element of the rare earth group, Syn. atomic number 64, Gd |
| holmium | (n) a trivalent metallic element of the rare earth group; occurs together with yttrium; forms highly magnetic compounds, Syn. Ho, atomic number 67 |
| neodymium | (n) a yellow trivalent metallic element of the rare earth group; occurs in monazite and bastnasite in association with cerium and lanthanum and praseodymium, Syn. atomic number 60, Nd |
| promethium | (n) a soft silvery metallic element of the rare earth group having no stable isotope; was discovered in radioactive form as a fission product of uranium, Syn. Pm, atomic number 61 |
| samarium | (n) a grey lustrous metallic element of the rare earth group; is used in special alloys; occurs in monazite and bastnasite, Syn. Sm, atomic number 62 |
| terbium | (n) a metallic element of the rare earth group; used in lasers; occurs in apatite and monazite and xenotime and ytterbite, Syn. Tb, atomic number 65 |
| thulium | (n) a soft silvery metallic element of the rare earth group; isotope 170 emits X-rays and is used in small portable X-ray machines; it occurs in monazite and apatite and xenotime, Syn. atomic number 69, Tm |
