Terbium

Terbium is a lanthanide, meaning it is a rare earth metal. It is soft and silver-grey. Its ability to be sliced with a knife gives hint of it's malleability and ductility. It has many interesting uses. Being used in areas such as the production of energy-saving light bulbs to cancer treatment, this element is not one to be overlooked. Its magnetic qualities even give way into new forms of nanotechnology.

Chemical Properties
Terbium is relatively stable in earth's atmosphere. However, it does react slowly with water and dissolves in acids.
 * Thermal conductivity: 11.1 J/m-sec-deg
 * Electrical conductivity: 8.8 1/mohm-cm
 * Polarizability: 25.5 A^3

Physical Properties
Terbium is a silver-grey metal. It is malleable, ductile, and can be cut with a knife. Terbium's atomic weight is 158.9254. The atomic structure of Terbium is hexagonal and tightly packed.
 * The density of Terbium at 293 K is 8.27 g/cm3.
 * Terbium's boiling point is 3041.0 °C (3314.15 K, 5505.8 °F).
 * Terbium's melting point is 1360.0 °C (1633.15 K, 2480.0 °F).
 * Heat of fusion: 10.80 kJ/mol
 * Electron affinity: 50 kJ/mole
 * Electronegativity: 1.21
 * Specific heat: 0.18 J/gK
 * Heat of vaporization: 330.90 kJ/mol
 * 1st ionization energy: 564.7 kJ/mole
 * 2nd ionization energy: 1112 kJ/mole
 * 3rd ionization energy: 2114 kJ/mole

Occurrences
Terbium is available commercially. It can be made in the laboratory, but it is difficult to isolate in its pure metal form. The lanthanides are normally found within certain minerals such as xenotime, monazite, and bastnaesite. The first two of the three are named orthophosphate minerals (LnPO4) and the third is a fluoride carbonate (LnCO3F). Even-numbered lanthanides are the more commonly found minerals. It is more difficult to remove terbium from monazite due to the presence of thorium, a radioactive product. Terbium is not always required to be fully removed from a compound, however, if full separation is called for, it can be very difficult to complete. Terbium is initially extracted as salts from the ore by extraction with the use of sulfuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern techniques of purification involve selective complexation techniques, solvent extractions, and ion exchange chromatography. Pure terbium can also be contrived though the reduction of TbF3 by the use of calcium metal.

$$2TbF3 + 3Ca → 2Tb + 3CaF2$$

Other calcium halides would work well, but the product CaF2 is easier to handle under the reaction conditions (50°C above the melting point of the element in an argon atmosphere). In this following table, ppb stands for parts per billion (1 billion =109).

It is listed in weight and in numbers of atoms. Values are difficult to determine so these numbers are not exact and should not be considered so. Terbium is present in the bones and kidneys of both humans and animals. Although Terbium is classified as a rare earth element, this term is misleading. Terbium is actually more prevalent than elements such as silver and mercury. Early chemists gave such elements the rare earth metal title due to the fact that they were hard to separate from other elements, thus they were rarely used. Terbium is one of the rarest of the lanthanides. It ranks around 55th among the elements in the Earth's crust. It's abundance can be compared to molybdenum and tungsten.

Isotopes
Elements can have a different number of neutrons. These different possible versions of the element are called isotopes. The only isotope of Terbium that occurs in nature is Terbium-159 ,however, there are many known radioactive isotopes of Terbium. In a radioactive isotope, the particles break apart and give off some form of radiation. The seventeen radioactive isotopes range from Terbium-147-158 and from 160-164. Terbium-149, for example, is used in medicine. The isotope is injected directly into cancer cells in the body. The radiation of Terbium-149 travels a short distance, so it can kill the cancer cells and damage few healthy ones. Therefore this isotope is a safer option than other radioactive sources.

Uses
The most common use of terbium and its compounds are generally in its phosphors. A phosphor gives off light when it is struck by an electron. Television screens are coated with different kinds of phosphors on the back. When electrons inside the television tubes strike the phosphors, they give off different colors of light. Phosphors containing terbium gives off green light.They are also used in X-ray screens to create clear pictures. Terbium's phosphorescent qualities allows for a smaller amount of time under an X-ray, causing less tissue damage. Fuel cells are manufactured using terbium. Terbium can use chemical reactions to create electricity, thus it is a fuel cell. Fuel cells, in the future, will be used as a source of electricity. Terbium fuel cells operate very efficiently at high temperatures. Terbium is also used in many magnetic devices. When you add it to certain alloys it forms magnetic devices which shrink or grow based on the strength and form of magnetic energy used. This is called magnetostrictive behavior. This has many technological uses. This could be used for small "motors" or "switches" in future nanotechnology. Terbium can also be used to stain cells which helps in certain laboratory experiments. It is also used in energy saving light bulbs due to its phosphorous qualities when used with the mercury discharge found in florescent strips. Terbium-149 radiation travels a short distance, so it can kill cancer cells and damage few healthy cells in cancer treatment. This is a safer option than other radioactive sources.

Discovery and History


Terbium was one element found during the great element hunt of the 1840s. In 1787, a Swedish army lieutenant, Carl Axel Arrhenius (1757-1824), encountered a strange black rock near the town of Ytterby, Sweden. Arrhenius gave this find to his chemist friend, Johan Gadolin (1760-1852). Gadolin analysed the rock, first finding an entire new mineral he named Yttria, after Ytterby. Later on, in 1843, Carl Gustav Mosander, another Swedish chemist, demonstrated that Yttria was really a mix of three minerals. He named them erbia, terbia, and yttria. The ending -a on these names indicates they are minerals found in the earth. This ending also usually refers to the presence of oxygen combined to other elements. However, due to the lack of technology, Mosanders research was unusually long and complicated. Many future chemists even mixed up erbia and terbia, due to lack of proper equipment. Mosander is given credit for discovering Terbium, however in 1886, Jean-Charles-Galissard de Marignac, a Frech chemist was the first to prepare pure terbium.

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Additional Information

 * Hybrid nanocomposites for nanotechnology Lhadi Merhar, Springer Science and Business Media LLC, 2009.
 * Layered double hydroxide nanoparticles incorporating terbium: applicability as a fluorescent probe and morphology modifierAnthony W. Musumeci1, Zhi Ping Xu1, Suzanne V. Smith2, Rodney F. Minchin3 and Darren J. Martin1, Springer Science and Business Media B.V LLC, 2009. 8 January 2009
 * Laser-induced anisotropy in terbium-gallium garnetX. Chen and S. Gonzalez, Laboratoire de Physique de l’Universit´e de Bourgogne, Facult´e des Sciences Springer-Verlag, 1998