Rare Earth Elements (Metals)

This is a list of rare earth elements (REEs), which are a special group of metals.

Key Takeaways: List of Rare Earth Elements

The rare earth elements (REEs) or rare earth metals (REMs) are a group of metals found within the same ores and possessing similar chemical properties.
Scientists and engineers disagree on exactly which element should be included in a list of the rare earths, but they generally include the fifteen lanthanide elements, plus scandium and yttrium.
Despite their name, the rare earths aren't actually rare with respect to abundance in the Earth's crust. The exception is promethium, a radioactive metal.

The CRC Handbook of Chemistry and Physics and IUPAC list the rare earths as consisting of the lanthanides, plus scandium and yttrium. This includes atomic number 57 through 71, as well as 39 (yttrium) and 21 (scandium):

Lanthanum (sometimes considered a transition metal)
Cerium
Praseodymium
Neodymium
Promethium
Samarium
Europium
Gadolinium
Terbium
Dysprosium
Holmium
Erbium
Thulium
Ytterbium
Lutetium
Scandium
Yttrium

Other sources consider the rare earths to be the lanthanides and actinides:

Lanthanum (sometimes considered a transition metal)
Cerium
Praseodymium
Neodymium
Promethium
Samarium
Europium
Gadolinium
Terbium
Dysprosium
Holmium
Erbium
Thulium
Ytterbium
Lutetium
Actinium (sometimes considered a transition metal)
Thorium
Protactinium
Uranium
Neptunium
Plutonium
Americium
Curium
Berkelium
Californium
Einsteinium
Fermium
Mendelevium
Nobelium
Lawrencium

Classification of Rare Earths

The classification of the rare earth elements is as hotly disputed as the list of included metals. One common method of classification is by atomic weight. Low atomic weight elements are the light rare earth elements (LREEs). Elements with high atomic weight are the heavy rare earth elements (HREEs). Elements that fall between the two extremes are the middle rare earth elements (MREEs). One popular system categorizes atomic numbers up to 61 as LREEs and those higher than 62 as HREEs (with the middle range absent or up to interpretation).

Summary of Abbreviations

Several abbreviations are used in connection with the rare earth elements:

RE: rare earth
REE: rare earth element
REM: rare earth metal
REO: rare earth oxide
REY: rare earth element and yttrium
LREE: light rare earth elements
MREE: middle rare earth elements
HREE: heavy rare earth elements

Rare Earth Uses

In general, the rare earths are used in alloys, for their special optical properties, and in electronics. Some specific uses of elements include:

Scandium: Use to make light alloys for the aerospace industry, as a radioactive tracer, and in lamps
Yttrium: Used in yttrium aluminum garnet (YAG) lasers, as a red phosphor, in superconductors, in fluorescent tubes, in LEDs, and as a cancer treatment
Lanthanum: Use to make high refractive index glass, camera lenses, and catalysts
Cerium: Use to impart a yellow color to glass, as a catalyst, as a polishing powder, and to make flints
Praseodymium: Used in lasers, arc lighting, magnets, flint steel, and as a glass colorant
Neodymium: Used to impart violet color to glass and ceramics, in lasers, magnets, capacitors, and electric motors
Promethium: Used in luminous paint and nuclear batteries
Samarium: Used in lasers, rare earth magnets, masers, nuclear reactor control rods
Europium: Used to prepare red and blue phosphors, in lasers, in fluorescent lamps, and as an NMR relaxant
Gadolinium: Used in lasers, x-ray tubes, computer memory, high refractive index glass, NMR relaxation, neutron capture, MRI contrast

Terbium: Use in green phosphors, magnets, lasers, fluorescent lamps, magnetostrictive alloys, and sonar systems
Dysprosium: Used in hard drive disks, magnetostrictive alloys, lasers, and magnets
Holmium: Use in lasers, magnets, and calibration of spectrophotometers
Erbium: Used in vanadium steel, infrared lasers, and fiber optics
Thulium: Used in lasers, metal halide lamps, and portable x-ray machines
Ytterbium: Used in infrared lasers, stainless steel, and nuclear medicine
Lutetium: Used in positron emission tomography (PET) scans, high refractive index glass, catalysts, and LEDs

Sources

Brownlow, Arthur H. (1996). Geochemistry. Upper Saddle River, N.J.: Prentice Hall. ISBN 978-0133982725.
Connelly, N. G. and T. Damhus, ed. (2005). Nomenclature of Inorganic Chemistry: IUPAC Recommendations 2005. With R. M. Hartshorn and A. T. Hutton. Cambridge: RSC Publishing. ISBN 978-0-85404-438-2.
Hammond, C. R. (2009). "Section 4; The Elements". In David R. Lide (ed.). CRC Handbook of Chemistry and Physics, 89th ed. Boca Raton, FL: CRC Press/Taylor and Francis.
Jébrak, Michel; Marcoux, Eric; Laithier, Michelle; Skipwith, Patrick (2014). Geology of mineral resources (2nd ed.). St. John's, NL: Geological Association of Canada. ISBN 9781897095737.
Ullmann, Fritz, ed. (2003). Ullmann's Encyclopedia of Industrial Chemistry. 31. Contributor: Matthias Bohnet (6th ed.). Wiley-VCH. p. 24. ISBN 978-3-527-30385-4.

Rare Earth Elements List

Elements in the Rare Earth Element Group