LANTHANUM (LA/57) & THE LANTHANIDE RARE EARTHS

last update 01 jul 24

* The lanthanide rare earths occupy a "side row" off of row 6 of the periodic table. The lanthanide rare earths are not necessarily rare; a good part of the list is more common than tin, it's just that their properties are so similar that they are hard to identify and extract.

The element yttrium is something of an oddity, since as far as its position in the periodic table goes, it's a transition metal. However, it is directly above the "side row" of the lanthanide rare earths in column 3 of the periodic table, and not very surprisingly yttrium's chemical behavior is very much like that of the lanthanide rare earths. Since yttrium is also often found in nature in ores with a strong association with lanthanide rare earths. It is generally referred to as a rare earth -- though this is doubly inexact, because it's twice as common as lead.

lanthanide rare earths in the periodic table

____________________________________________________________________ YTTRIUM / Y / 39 A soft, silvery-white metal, stable in air because it forms a protective oxide layer. It reacts with water to release hydrogen gas. Only one isotope is found in nature, Y<89/39>; it is stable. atomic weight: 88.90585 abundance: 28th density: 4.469 gm/cc melting point: 1,522 C boiling point: 5,338 C valence: 3 ____________________________________________________________________ LANTHANUM / La / 57 A cheese-soft, silvery-white reactive metal. The primary isotope is La<138/57>, making up 99.9% of accumulations found in nature. The remainder is La<138/57>, which is just barely radioactive, with a half-life of 100 billion years. atomic weight: 138.055 abundance: 28th density: 6.145 gm/cc melting point: 918 C boiling point: 3,464 C valence: 3 ____________________________________________________________________ CERIUM / Ce / 58 A gray, highly reactive metal. Four isotopes are found in nature: Ce<140/58> / 88.5% Ce<142/58> / 11% Ce<138/58> / 0.3% Ce<136/58> / 0.2%. All are stable, except Ce<142/58>, which has a half-life of about 5E^16 years, longer than the age of the Universe. atomic weight: 140.116 abundance: 25th density: 6,770 gm/cc melting point: 798 C boiling point: 3,443 C valence: 3 4 ____________________________________________________________________ PRASEODYMIUM / Pr / 59 A soft, malleable, silvery, reactive metal. It has one stable isotope, Pr<141/59>; all the unstable isotopes are highly radioactive, with the longest-lived, Pr<143/59>, having a half-life of only 13.57 days. atomic weight: 140.90765 abundance: 39th density: 6.773 gm/cc melting point: 931 C boiling point: 3,520 C valence: 3 ____________________________________________________________________ NEODYMIUM / Nd / 60 A bright silvery-white, moderately reactive metal. It is almost as common as copper. There are seven isotopes found in nature: Nd<152/60> / 27% Nd<144/60> / 24% Nd<146/60> / 17% Nd<143/60> / 12% Nd<145/60> / 8% Nd<148/60> / 6% Nd<150/60> / 6% All are stable, except for Nd<144/60>, with a half-life of 2E15 years, and Nd<150/60>, with a half-life of 1.1E19 years. atomic weight: 144.24 abundance: 26th density: 7.008 gm/cc melting point: 1,021 C boiling point: 3,074 C valence: 3 ____________________________________________________________________ PROMETHIUM / Pm / 61 Unlike the other lanthanide rare earths, promethium is inherently radioactive and essentially not found in nature. There are several dozen known isotopes, the most stable being Pm<145/61> with a half-life of 17.7 years (though some sources claim 2.6 years). atomic weight: 145 abundance: negligible density: 7.22 gm/cc melting point: 1,042 C boiling point: ~3,000 C valence: 3 ____________________________________________________________________ SAMARIUM / Sm / 62 A silvery-white metal that will form an oxide layer in moist air. It will burn if heated to 150 degrees Celsius. Seven isotopes are found in nature: Sm<152/62> / 27% Sm<154/62> / 23% Sm<147/62> / 15% Sm<149/62> / 14% Sm<148/62> / 11% Sm<150/62> / 7% Sm<144/62> / 3% Sm<149/62> and Sm<148/62> are both unstable with half-lives of more than 10^15 years, while Sm<147/62> is unstable with a half life of about 10^11 years. The other four isotopes in the list are stable. atomic weight: 150.36 abundance: 40th density: 7.52 gm/cc melting point: 1,074 C boiling point: 1,794 C valence: 2 3 ____________________________________________________________________ EUROPIUM / Eu / 63 A soft, silvery metal, the most reactive of the lanthanides; it will burn spontaneously in air at 180 degrees Celsius. Two isotopes are found in nature: Eu<153/63> / 52% Eu<151/63> / 48%. Both are stable. atomic weight: 151.965 abundance: 50th density: 5.244 gm/cc melting point: 822 C boiling point: 1,527 C valence: 2 3 ____________________________________________________________________ GADOLINIUM / Gd / 64 A soft, shiny, silvery, moderately reactive metal. There are seven naturally occurring isotopes, including: Gd<158/64> / 25% Gd<160/64> / 22% Gd<156/64> / 20.4% Gd<157/64> / 15.6% Gd<155/64> / 15% Gd<154/64> / 2% Gd<152/64> / 0.2% All are stable except for Gd<152/64>, though it has a very long halflife of 1.1E14 years. atomic weight: 157.25 abundance: 41st density: 7.9 gm/cc melting point: 1,313 C boiling point: 3,273 C valence: 3 ____________________________________________________________________ TERBIUM / Tb / 65 A cheese-soft silvery metal, it is slow to oxidize in air but will react at a moderate rate in water. The only isotope found in nature is Tb<159/65>, which is stable. atomic weight: 158.92534 abundance: 57th density: 8.23 gm/cc melting point: 1,356 C boiling point: 3,230 C valence: 3 4 ____________________________________________________________________ DYSPROSIUM / Dy / 66 A bright, silvery metal that oxidizes slowly in air, reacts with cold water, and dissolves quickly in acid. Seven isotopes occur in nature: Dy<164/66> / 28% Dy<162/66> / 26.5% Dy<163/66> / 25% Dy<161/66> / 19% Dy<160/66> / 2.5% Dy<158/66> / 0.1% Dy<156/66> / 0.06% All are stable. atomic weight: 162.50 abundance: 42nd density: 8.55 gm/cc melting point: 1,412 C boiling point: 2,567 C valence: 3 ____________________________________________________________________ HOLMIUM / Ho / 67 A bright, soft, silvery metal that is slowly attacked by oxygen or water, and dissolves in acids. All holmium found in nature is the stable isotope Ho<165/67>. atomic weight: 164.93032 abundance: 56th density: 8.795 gm/cc melting point: 1,470 C boiling point: 2,700 C valence: 3 ____________________________________________________________________ ERBIUM / Er / 68 A bright, silvery metal that is slowly attacked by oxygen or water, and dissolves in acids. Six isotopes are found in nature: Er<166/68> / 33.5% Er<168/68> / 27% Er<167/68> / 23% Er<170/68> / 15% Er<164/68> / 1.5% Er<162/68> / 0.1% All are stable. atomic weight: 167.26 abundance: 44th density: 9.1 gm/cc melting point: 1,529 C boiling point: 2,868 C valence: 3 ____________________________________________________________________ THULIUM / Tm / 69 A bright, cheese soft, silvery metal that is slowly tarnishes in air and reacts with water. All thulium found in nature is the stable isotope Th<169/69>. atomic weight: 168.93421 abundance: 61st density: 9.321 gm/cc melting point: 1,545 C boiling point: 1,950 C valence: 3 ____________________________________________________________________ YTTERBIUM / Yb / 70 A soft, silvery-white metal that is slowly tarnishes in air to form a protective oxide layer, but dissolves easily in acids. Seven isotopes are found in nature: Yb<174/70> / 32% Yb<172/70> / 22% Yb<173/70> / 16% Yb<171/70> / 14.5% Yb<176/70> / 12.5% Yb<170/70> / 3% Yb<168/70> / 0.1% All are stable. atomic weight: 173.04 abundance: 43rd density: 6.965 gm/cc melting point: 819 C boiling point: 1,196 C valence: 2 3 ____________________________________________________________________ LUTETIUM / Lu / 71 A silvery-white metal, resistant to corrosion and the hardest of the rare earths. Technically, it is actually part of the transition metal series, but its properties are close enough to those of the other lanthanide rare earths to permit it to be included with them. Two isotopes are found in nature: stable Lu<175/71> at 97.5% and radioactive Lu<176/71> at 2.5%, with a half-life of 20 billion years. atomic weight: 174.967 abundance: 60th density: 9.841 gm/cc melting point: 1,663 C boiling point: 3,402 C valence: 3 ____________________________________________________________________

The lanthanide rare earths in general have niche uses; levels of production range from:

A few tens of thousands of tonnes a year for cerium and a little over ten thousand tonnes a year for lanthanum.
A hundred to a few hundreds of tonnes a year for yttrium, samarium, europium, gadolinium, dysprosium, and erbium.
Tens of tonnes a year for terbium, holmium, thulium, ytterbium, and lutetium.

Refining rare earths tends to be a "dirty" process, and for a time China, with weak environmental regulations, was effectively the sole source of them. Chinese attempts to restrict sales of rare earths and rising demand led to a resuscitation of rare-earth extraction in the US and elsewhere -- though that led in turn to a glut and a scale-back. Applications of the lanthanides include:

Magnetic alloys. Neodymium is used as a component to high-quality magnetic alloys, such as "NIB": neodymium, iron, and boron. Samarium-cobalt alloys were once used for this purpose, but they have been largely replaced by NIB -- except for high-temperature applications, since samarium-cobalt alloy retains its magnetism at higher temperatures.

Dysprosium and holmium are used as minor components of magnetic alloys, Yttrium-indium-garnet (YIG) is used in a number of electronic applications, such as magnetic recording heads and filter components in microwave systems. Gadolinium is also used in magnetic recording heads.
Additives to ceramics and glass. Praesodymium oxide gives a yellow coloring to glass, while neodymium oxide gives a deep purple coloring. Cerium oxide added to glass screens out ultraviolet, while samarium oxide and erbium oxide will screen out infrared. Yttrium oxide (Y2O3) is used in ruggedized glass, often for camera lenses.
TV display phosphors and components of "lasing mixtures" in lasers. Europium is used as a red phosphor element; neodymium is commonly used in lasers; and yttrium-aluminum-garnet (YAG) crystals are used in high-powered lasers.

Yttrium is used in a number of alloys, conferring various properties such as improved casting ability, finer grain, and heat resistance, depending on the alloy. Cerium oxide is a common component of catalytic systems, making it the most widely used of the lanthanides. Dysprosium is used in high-intensity halide lamps. Gadolinium has an unusually strong capability to absorb neutrons and so it is used in the control rods of nuclear reactor cores. Promethium is very radioactive and its only use is as a radiation source. Terbium, thulium, ytterbium, and lutetium are rare -- lutetium is the most expensive of all metals -- and only used in small amounts in some very specialized applications; other lanthanide rare earths are used in their place whenever possible.