A lanthanide is any member of a group (called the lanthanum series) of rare, metallic elements with atomic numbers from 57 (lanthanum) to 71 (lutetium) inclusive, in which the 4f orbitals are being filled (Figure 1). The lanthanides are: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Because their electronic structures are very similar, differing only in inner orbitals, the properties of the lanthanides are all very similar. The lanthanides are all reactive metals resembling scandium, forming trivalent salts and ligand complexes. Cerium, praseodymium, and terbium also form tetravalent compounds, and europium, ytterbium, and samarium form divalent ones. All form divalent ionic hydrides and sulfides.

 

There is a decrease (the lanthanide contraction) in ionic radii through the series, so that the third row transition element following the lanthanides have ionic radii almost identical to those of their analogues in the second row, and hence have similar properties.

 

The lanthanides are separated by chromatography and ion-exchange resins. They are used in alloys, including misch metal; and their compounds (mixed or separately) are used as abrasives, for making glasses and ceramics, as "getters," as catalysts in the petroleum industry, and to make phosphors, lasers, and microwave devices.

 

Except for promethium, the lanthanides are not uncommon – the normal source is monazite which contains 90% La, Ce, Pr, Nd in its lanthanide contents.

 

See also rare earth elements.

 

Cerium

Cerium (Ce) is a soft, ductile, iron-gray metallic element, the most abundant of the lanthanides (and more abundant than tin or lead) (Figure 2). It was first isolated by J. J. Berzelius and W. Hisinger in Vestmanland, Sweden, in 1803, and is named after the asteroid Ceres, discovered in 1801. The chief ore is monazite. Cerium is used in making pocket lighter flints), in alloys, catalysts, nuclear fuels, and special glass and ceramics, and as the core of carbon electrodes in arc lamps. However, its use is restricted by the fact that it tarnishes easily, reacts with water, and burns when heated. Its most common isotope is ¹⁴⁰Ce (88.48%).

 

atomic number	58
relative atomic mass	140.12
relative density	6.77
melting point	798°C (1,468°F)
boiling point	3,257°C (5,895°F)

 

Dysprosium

Dysprosium (Dy) is a silver-white metallic element of the lanthanide series (Figure 3). Discovered by P. E. Lecoq de Boisbaudran in Paris in 1886, its name comes from the Greek dysprositos meaning "hard to get". Its chief ores are monazite and bastnaesite. Its capacity to absorb neutrons makes it important in nuclear reactor control systems; dysprosium is also in making alloys for magnets and its compounds are used in lasers. Its most common isotope is ¹⁶⁴Dy (28.18%).

atomic number	66
relative atomic mass	162.5
relative density	8.54
melting point	1,409°C (2,568°F)
boiling point	2,335°C (4,235°F)

 

Erbium

Erbium (Er) is a silvery, metallic element of the lanthanide series, discovered by C. G. Mosander in Stockholm in 1843 (Figure 4). It is named after the Swedish town of Ytterby, where the mineral from which it was first isolated was found. There are six naturally occurring isotopes, and the chief ores are monazite and bastnaesite. Twelve radioactive isotopes have been identified. Soft and malleable, erbium is used in specialized alloys, and erbium oxide is used as a pink colorant for glass. Its most common isotope is ¹⁶⁶Er (33.41%).

atomic number	68
relative atomic mass	167.26
relative density	9.045
melting point	1,522°C (2,772°F)
boiling point	2,863°C (5,185°F)

 

Europium

Europium (Eu) is a silver-white, metallic element of the lanthanide series, being the softest and most volatile member (Figure 5). It was first isolated as the oxide in 1896; the element itself was discovered by E. A. Demarçay in Paris in 1901 . Its chief ores are monazite and bastnaesite. Europium is used in the manufacture of color television screens, lasers, thin superconducting alloys, and control rods in nuclear reactors. Its most common isotope is ¹⁵³Eu (52.18%).

atomic number	63
relative atomic mass	151.96
relative density	5.25
melting point	822°C (1,512°F)
boiling point	1,597°C (2,907°F)

 

Gadolinium

Gadolinium (Gd) is a white metallic element of the lanthanide series, first isolated as the oxide in 1880 by J. C. Galissard de Marignac in Geneva (Figure 6). It is named after the Finnish chemist J. Gadolin. Chief ores are gadolinite, monazite, and bastnaesite. A malleable and ductile metal, its specialized uses include neutron absorption (important in many nuclear reactors) and the manufacture of certain alloys for making magnets and in the recording heads of video recorders. Its most common isotope is ¹⁵⁸Gd (24.87%).

atomic number	64
relative atomic mass	157.25
relative density	7.898
melting point	1,311°C (2,392°F)
boiling point	3,233°C (5,851°F)

 

Holmium

Holmium (Ho) is a metallic element of the lanthanide series (Figure 7), first identified spectroscopically in 1878 by P. T. Cleve in Uppsala, Sweden, and independently by M. Delafontaine and J. L. Soret in Geneva. Its chief ore is monazite (a phosphate). Alloys of holmium are in used in magnets but the element has few commercial uses. Its most common isotope is ¹⁶⁵Ho (100%).

 

atomic number	67
relative atomic mass	164.93
relative density	8.803
melting point	1,470°C (2,680°F)
boiling point	2,720°C (4,930°F)

 

Lanthanum

Lanthanum (La) is a silver-white metallic element that is the prototype and second most abundant member of the lanthanide series (Figure 8). First identified by C. G. Mosander in Stockholm in 1839, its name comes from the Latin lanthana meaning 'to lie hidden.' Its chief ores are monazite and bastnaesite. Soft, malleable, and ductile, lanthanum is used as a catalyst in cracking crude oil, in alloys, and to manufacture optical glasses. Its most common isotope is ¹³⁹La (99.91%).

 

atomic number	57
relative atomic mass	138.906
relative density	6.17
melting point	920°C (1,688°F)
boiling point	3,454°C (6,249°F)

 

Lutetium

Lutetium (Lu) is a metallic element of the lanthanide series, first isolated by G. Urbain in Paris in 1906 (and independently by C. James in New Hampshire), together with ytterbium (Figure 9). Its name comes from Lutetia, the Latin word for Paris. Its chief ore is monazite. The element is used as a catalyst, but has no other commercial uses. Its most common isotope is ¹⁷⁵Lu (97.41%).

 

atomic number	71
relative atomic mass	174.97
relative density	9.842
melting point	1,656°C (3,013°F)
boiling point	3,315°C (5,999°F)

 

Neodymium

Neodymium (Nd) is a silver-yellow metallic element of the lanthanide series (Figure 10). It was first isolated in the form of its oxide in 1885 and the pure metal was first obtained in 1925. Chief ores are monazite and bastnaesite. Neodymium is used to manufacture lasers, and its salts are used to color glass. Its most common isotope is ¹⁴²Nd (27.11%).

 

atomic number	60
relative atomic mass	144.24
relative density	7.004
melting point	1,010°C (1,850°F)
boiling point	3,068°C (5,554°F)

 

Praseodymium

Praseodymium (Pr) is a silver-yellow metallic element of the lanthanide series, first isolated in 1885 (Figure 11). Its chief ores are monazite and bastnaesite. Soft, malleable, and ductile praseodymium is used in carbon electrodes for arc lamps. Its most common isotope is ¹⁴¹Pr (100%).

 

atomic number	59
relative atomic mass	140.908
relative density	6.77
melting point	931°C (1,708°F)
boiling point	3,512°C (6,354°F)

 

Promethium

Promethium (Pm) is a radioactive, metallic element of the lanthanide series. It was first made in 1941 by particle bombardment of neodymium and praseodymium. Promethium occurs in uranium ores in minute amounts. The isotope ¹⁴⁷Pm is used in phosphorescent paints, X-ray tubes, and in nuclear-powered batteries for space vehicles. The most stable isotope is ¹⁴⁵Pm (half-life 17.7 years).

 

atomic number	61
melting point	1,080°C (1,976°F)
boiling point	2,460°C (4,460°F)

 

Samarium

Samarium (Sm) is a gray-white metallic element of the lanthanide series, first identified spectroscopically in 1879 (Figure 12). Its chief ores are monazite and bastnaesite. Samarium is used in carbon-arc lamps, as a moderator in nuclear reactors, and as a catalyst. Some samarium alloys are used for making powerful permanent magnets. Samarium's most common isotope is ¹⁵²Sm (26.72%).

 

atomic number	62
relative atomic mass	150.35
relative density	7.52
melting point	1,072°C (1,962°F)
boiling point	3,791°C (3,256°F)

 

Terbium

Terbium (Tb) is a silver-gray metallic element of the lanthanide series (Figure 13). Discovered in 1843, it is found in such minerals as monazite, gadolinite, and apatite. The soft element is used in semiconductors; sodium terbium borate is used in lasers. Its single natural isotope is ¹⁵⁹Tb .

 

atomic number	65
relative atomic mass	158.925
relative density	8.234
melting point	1,360°C (2,480°F)
boiling point	3,041°C (5,506°F)

 

Thulium

Thulium (Tm) is a lustrous, silver-white, metallic element and the least abundant member of the lanthanide series (Figure 14). First discovered in 1879, its chief ore is monazite. Soft, malleable, and ductile, thulium combines with oxygen and the halogens. It is used in arc lighting; thulium-170, which emits X-rays, is used in portable X-ray units. Its most common isotope is ¹⁶⁹Tm (100%).

 

atomic number	69
relative atomic mass	168.934
relative density	9.31
melting point	1,545°C (2,813°F)
boiling point	1,947°C (3,537°F)

 

Ytterbium

Ytterbium (Yb) is a silver-white, metallic element of the lanthanide series (Figure 15). First isolated in 1878, ytterbium's chief ore is monazite. The shiny, soft element is used to produce steel and other alloys. Its most common isotope is ¹⁷⁴Yb (31.84%).

 

In 2009,a team of scientists announced it had managed to teleport a single ion of ytterbium – a world's first. Previously, teleportation had been restricted to photons. The group conducted teleportation between two ions of ytterbium (Yb+): an original that held a unique quantum state, and a second 'blank' target ion.¹

 

atomic number	70
relative atomic mass	173.04
relative density	6.97
melting point	824°C (1,515°F)
boiling point	1,193°C (2,179°F)

 

Reference

1. Olmschenk, S. et al. Science 323, 486–489 (2009).