| 1 | 21 | Sc | Scandium | from LatinScandia (Scandinavia). | Light aluminium-scandium alloys for aerospace components, additive in metal-halide lamps and mercury-vapor lamps,[7] radioactive tracing agent in oil refineries | 22[8] |
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| 2 | 39 | Y | Yttrium | after the village of Ytterby, Sweden, where the first rare earth ore was discovered. | Yttrium aluminium garnet (YAG) laser, yttrium vanadate (YVO4) as host for europium in television red phosphor, YBCOhigh-temperature superconductors, yttria-stabilized zirconia (YSZ), yttrium iron garnet (YIG) microwave filters,[7] energy-efficient light bulbs (part of triphosphor white phosphor coating in fluorescent tubes, CFLs and CCFLs, and yellow phosphor coating in white LEDs),[9]spark plugs, gas mantles, additive to steel, cancer treatments | 33[8] |
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| 3 | 57 | La | Lanthanum | from the Greek "lanthanein", meaning to be hidden. | High refractive index and alkali-resistant glass, flint, hydrogen storage, battery-electrodes, camera lenses, fluid catalytic cracking catalyst for oil refineries | 39[8] |
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| 4 | 58 | Ce | Cerium | after the dwarf planet Ceres, named after the Roman goddess of agriculture. | Chemical oxidizing agent, polishing powder, yellow colors in glass and ceramics, catalyst for self-cleaning ovens, fluid catalytic cracking catalyst for oil refineries, ferrocerium flints for lighters, robust intrinsically hydrophobic coatings for turbine blades. | 66.5[8] |
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| 5 | 59 | Pr | Praseodymium | from the Greek "prasios", meaning leek-green, and "didymos", meaning twin. | Rare-earth magnets, lasers, core material for carbon arc lighting, colorant in glasses and enamels, additive in didymium glass used in welding goggles,[7]ferrocerium firesteel (flint) products. | 9.2[8] |
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| 6 | 60 | Nd | Neodymium | from the Greek "neos", meaning new, and "didymos", meaning twin. | Rare-earth magnets, lasers, violet colors in glass and ceramics, didymium glass, ceramic capacitors, electric motors of electric automobiles | 41.5[8] |
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| 7 | 61 | Pm | Promethium | after the TitanPrometheus, who brought fire to mortals. | Nuclear batteries, luminous paint | 1×10−15[10] |
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| 8 | 62 | Sm | Samarium | after mine official, Vasili Samarsky-Bykhovets. | Rare-earth magnets, lasers, neutron capture, masers, control rods of nuclear reactors | 7.05[8] |
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| 9 | 63 | Eu | Europium | after the continent of Europe. | Red and blue phosphors, lasers, mercury-vapor lamps, fluorescent lamps, NMRrelaxation agent | 2[8] |
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| 10 | 64 | Gd | Gadolinium | after Johan Gadolin (1760–1852), to honor his investigation of rare earths. | High refractive index glass or garnets, lasers, X-ray tubes, computer memories, neutron capture, MRI contrast agent, NMR relaxation agent, magnetostrictive alloys such as Galfenol, steel additive | 6.2[8] |
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| 11 | 65 | Tb | Terbium | after the village of Ytterby, Sweden. | Additive in Neodymium based magnets, green phosphors, lasers, fluorescent lamps (as part of the white triband phosphor coating), magnetostrictive alloys such as terfenol-D, naval sonar systems, stabilizer of fuel cells | 1.2[8] |
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| 12 | 66 | Dy | Dysprosium | from the Greek "dysprositos", meaning hard to get. | Additive in Neodymium based magnets, lasers, magnetostrictive alloys such as terfenol-D, hard disk drives | 5.2[8] |
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| 13 | 67 | Ho | Holmium | after Stockholm (in Latin, "Holmia"), native city of one of its discoverers. | Lasers, wavelength calibration standards for optical spectrophotometers, magnets | 1.3[8] |
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| 14 | 68 | Er | Erbium | after the village of Ytterby, Sweden. | Infrared lasers, vanadium steel, fiber-optic technology | 3.5[8] |
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| 15 | 69 | Tm | Thulium | after the mythological northern land of Thule. | Portable X-ray machines, metal-halide lamps, lasers | 0.52[8] |
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| 16 | 70 | Yb | Ytterbium | after the village of Ytterby, Sweden. | Infrared lasers, chemical reducing agent, decoy flares, stainless steel, stress gauges, nuclear medicine, monitoring earthquakes | 3.2[8] |
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| 17 | 71 | Lu | Lutetium | after Lutetia, the city that later became Paris. | Positron emission tomography – PET scan detectors, high-refractive-index glass, lutetium tantalate hosts for phosphors, catalyst used in refineries, LED light bulb | 0.8[8] |
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(20min delay)