At A Glance: Tb

Atomic Number: 65
Atomic Symbol: Tb
Atomic Weight: 158.9254
Electron Configuration: [Xe]6s24f9
Atomic Radius: 221 pm (Van der Waals)
Melting Point: 1356 °C
Boiling Point: 3230 °C
Oxidation States: 3
Sources: Terbium is never found in nature as a free element, but it is contained in many minerals, including cerite, gadolinite, monazite, xenotime and euxenite.Uses: Energy efficient fluorescent lighting, magneto-optic recording of data, solid-state devices, and fuel cells.

Content provided by Los Alamos National Laboratory. Used with permission.

Rare earth element - Terbium
Rare earth element - Terbium
Terbium Spin Video

Photos of rare earth elements used on our site are copyright of Max Whitby and Theodore Gray. Used with permission.

Terbium helps enable energy efficient fluorescent lamps, and Terbium metal alloys help to provide suitable metallic films for magneto-optic recording of data. Sodium terbium borate is used in solid-state devices. It can be used with ZrO2 as a crystal stabilizer of fuel cells which operate at elevated temperature.


Discovered by Mosander in 1843. Terbium is a member of the lanthanide or “rare earth” group of elements. It is found in cerite, gadolinite, and other minerals along with other rare earths. It is recovered commercially from monazite in which it is present to the extent of 0.03%, from xenotime, and from euxenite, a complex oxide containing 1% or more of terbia.


Terbium has been isolated only in recent years with the development of ion-exchange techniques for separating the rare-earth elements. As with other rare earth metals, it can be produced by reducing the anhydrous chloride or fluoride with calcium metal in a tantalum crucible. Calcium and tantalum impurities can be removed by vacuum remelting. Other methods of isolation are possible.


Terbium is reasonably stable in air. It is a silver-gray metal, and is malleable, ductile, and soft enough to be cut with a knife. Two crystal modifications exist, with a transformation temperature of 1289°C. Twenty one isotopes with atomic masses ranging from 145 to 165 are recognized. The oxide is a chocolate or dark maroon color.


Little is known of the toxicity of terbium. It should be handled with care as with other lanthanide element.

Sources: Los Alamos National Laboratory; Molycorp

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