Terbium: the essentials

Terbium is reasonably stable in air. It is a silvery-grey metal, and is malleable, ductile, and soft enough to be cut with a knife. It is a rare earth metal found in cerite, gadolinite and monazite. The element itself was isolated only recently.

This sample is from The Elements Collection, an attractive and safely packaged collection of the 92 naturally occurring elements that is available for sale.

Terbium: historical information

Terbium was discovered by Gustav Mosander in 1843. He detected it is as an impurity in yttria which is yttrium oxide, Y₂O₃.

Terbium around us Read more »

Terbium has no biological role.

Lutetium is never found in nature as the free element. Lutetium is found in the ore monazite sand [(Ce, La, etc.)PO₄], an ore containing small amounts of all the rare earth metals. Other minerals containing terbium include cerite, gadolinite, xenotime, and euxenite. It is difficult to separate from other rare earth elements.

Abundances for terbium in a number of different environments. More abundance data »

Location	ppb by weight	ppb by atoms	Links
Universe	0.5	0.004
Crustal rocks	940	120
Human	(no data) ppb by weight	(no data) atoms relative to C = 1000000

Physical properties Read more »

• Density of solid: 8219 kg m^-3
• Molar volume: 19.30 cm³
• Thermal conductivity: 11 W m^‑1 K^‑1

Heat properties Read more »

• Melting point: 1629 [1356 °C (2473 °F)] K
• Boiling point: 3503 [3230 °C (5846 °F)] K
• Enthalpy of fusion: 10.8 kJ mol^-1

Crystal structure Read more »

The solid state structure of terbium is: hcp (hexagonal close-packed).

Terbium: orbital properties Read more »

Terbium atoms have 65 electrons and the shell structure is 2.8.18.27.8.2. The ground state electronic configuration of neutral Terbium is [Xe].4f⁹.6s² and the term symbol of Terbium is ⁶H_15/2.

• Pauling electronegativity: (no data) (Pauling units)
• First ionisation energy: 565.8 kJ mol^‑1
• Second ionisation energy: 1110 kJ mol^‑1

Isolation

Isolation: terbium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO₄ (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO₃F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.

For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H₂SO₄), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.

Pure terbium is available through the reduction of TbF₃ with calcium metal.

2TbF₃ + 3Ca → 2Tb + 3CaF₂

This would work for the other calcium halides as well but the product CaF₂ is easier to handle under the reaction conditions (heat to 50°C above the melting point of the element in an argon atmosphere). Excess calcium is removed from the reaction mixture under vacuum.

Terbium isotopes Read more »

Table. Stables isotopes of terbium.

Isotope	Mass /Da	Natural abund. (atom %)	Nuclear spin (I)	Nuclear magnetic moment (μ/μN)
159Tb	158.925342 (4)	100	3/2	2.014