Difference between revisions of "Terbium" - New World Encyclopedia
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== Notable characteristics == | == Notable characteristics == | ||
− | Terbium is malleable, ductile, and soft enough to be cut with a knife. It is reasonably stable in air, and two crystal [[Allotropy|allotropes]] exist, with a transformation temperature of 1,289 °C. | + | Terbium is an [[inner transition metal]] (or [[lanthanide]]) that lies in period 6 of the [[periodic table]], between [[gadolinium]] and [[dysprosium]]. It is malleable, ductile, and soft enough to be cut with a knife. It is reasonably stable in air, and two crystal [[Allotropy|allotropes]] exist, with a transformation temperature of 1,289 °C. |
=== Isotopes === | === Isotopes === |
Revision as of 19:28, 22 February 2007
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General | ||||||||||||||||||||||||||||
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Name, Symbol, Number | terbium, Tb, 65 | |||||||||||||||||||||||||||
Chemical series | lanthanides | |||||||||||||||||||||||||||
Group, Period, Block | n/a, 6, f | |||||||||||||||||||||||||||
Appearance | silvery white | |||||||||||||||||||||||||||
Atomic mass | 158.92535(2) g/mol | |||||||||||||||||||||||||||
Electron configuration | [Xe] 4f9 6s2 | |||||||||||||||||||||||||||
Electrons per shell | 2, 8, 18, 27, 8, 2 | |||||||||||||||||||||||||||
Physical properties | ||||||||||||||||||||||||||||
Phase | solid | |||||||||||||||||||||||||||
Density (near r.t.) | 8.23 g/cm³ | |||||||||||||||||||||||||||
Liquid density at m.p. | 7.65 g/cm³ | |||||||||||||||||||||||||||
Melting point | 1629 K (1356 °C, 2473 °F) | |||||||||||||||||||||||||||
Boiling point | 3503 K (3230 °C, 5846 °F) | |||||||||||||||||||||||||||
Heat of fusion | 10.15 kJ/mol | |||||||||||||||||||||||||||
Heat of vaporization | 293 kJ/mol | |||||||||||||||||||||||||||
Heat capacity | (25 °C) 28.91 J/(mol·K) | |||||||||||||||||||||||||||
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Atomic properties | ||||||||||||||||||||||||||||
Crystal structure | hexagonal | |||||||||||||||||||||||||||
Oxidation states | 3, 4 (weakly basic oxide) | |||||||||||||||||||||||||||
Electronegativity | ? 1.2 (Pauling scale) | |||||||||||||||||||||||||||
Ionization energies (more) |
1st: 565.8 kJ/mol | |||||||||||||||||||||||||||
2nd: 1110 kJ/mol | ||||||||||||||||||||||||||||
3rd: 2114 kJ/mol | ||||||||||||||||||||||||||||
Atomic radius | 175 pm | |||||||||||||||||||||||||||
Atomic radius (calc.) | 225 pm | |||||||||||||||||||||||||||
Miscellaneous | ||||||||||||||||||||||||||||
Magnetic ordering | ferromagnetic in dry ice [1] | |||||||||||||||||||||||||||
Electrical resistivity | (r.t.) (α, poly) 1.150 µΩ·m | |||||||||||||||||||||||||||
Thermal conductivity | (300 K) 11.1 W/(m·K) | |||||||||||||||||||||||||||
Thermal expansion | (r.t.) (α, poly) 10.3 µm/(m·K) | |||||||||||||||||||||||||||
Speed of sound (thin rod) | (20 °C) 2620 m/s | |||||||||||||||||||||||||||
Speed of sound (thin rod) | (r.t.) (α form) 55.7 m/s | |||||||||||||||||||||||||||
Shear modulus | (α form) 22.1 GPa | |||||||||||||||||||||||||||
Bulk modulus | (α form) 38.7 GPa | |||||||||||||||||||||||||||
Poisson ratio | (α form) 0.261 | |||||||||||||||||||||||||||
Vickers hardness | 863 MPa | |||||||||||||||||||||||||||
Brinell hardness | 677 MPa | |||||||||||||||||||||||||||
CAS registry number | 7440-27-9 | |||||||||||||||||||||||||||
Notable isotopes | ||||||||||||||||||||||||||||
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Terbium (chemical symbol Tb, atomic number 65) is a silvery-white rare earth metal.[1]
Occurrence
Terbium is never found in nature as the free element, but it is contained in many minerals. For instance, it occurs in cerite, gadolinite, monazite ((Ce,La,Th,Nd,Y)PO4, which contains up to 0.03% of terbium), xenotime (YPO4) and euxenite ((Y,Ca,Er,La,Ce,U,Th)(Nb,Ta,Ti)2O6, which contains 1% or more of terbium).
History
Terbium was discovered in 1843 by Swedish chemist Carl Gustaf Mosander, who detected it as an impurity in Yttrium-oxide, Y2O3, and named after the village Ytterby in Sweden. It was not isolated in pure form until the recent advent of ion exchange techniques.
Terbium is classified as a rare earth element. The term "rare" is misleading because terbium is more common than metals such as silver and mercury. The name "rare earth" meant something else to early chemists. It was used because the rare earth elements were very difficult to separate from each other. They were not "rare" in the Earth, but they were "rarely" used for anything.
Notable characteristics
Terbium is an inner transition metal (or lanthanide) that lies in period 6 of the periodic table, between gadolinium and dysprosium. It is malleable, ductile, and soft enough to be cut with a knife. It is reasonably stable in air, and two crystal allotropes exist, with a transformation temperature of 1,289 °C.
Isotopes
Naturally occurring terbium is composed of 1 stable isotope, 159-Tb. 33 radioisotopes have been characterized, with the most stable being 158-Tb with a half-life of 180 years, 157-Tb with a half-life of 71 years, and 160-Tb with a half-life of 72.3 days. All of the remaining radioactive isotopes have half-lifes that are less than 6.907 days, and the majority of these have half lifes that are less than 24 seconds. This element also has 18 meta states, with the most stable being 156m1-Tb (t½ 24.4 hours), 154m2-Tb (t½ 22.7 hours) and 154m1-Tb (t½ 9.4 hours).
The primary decay mode before the most abundant stable isotope, 159-Tb, is electron capture, and the primary mode after is beta minus decay. The primary decay products before 159-Tb are element Gd (gadolinium) isotopes, and the primary products after are element Dy (dysprosium) isotopes.
Compounds
Terbium compounds include:
See also terbium compounds.
Applications
Terbium is used to dope calcium fluoride, calcium tungstate and strontium molybdate, materials that are used in solid-state devices, and as a crystal stabilizer of fuel cells which operate at elevated temperatures, together with ZrO2. Terbium is also used in alloys and in the production of electronic devices, its oxide is used in green phosphors in fluorescent lamps and color TV tubes. Sodium terbium borate is used in solid state devices.
Precautions
As with the other lanthanides, terbium compounds are of low to moderate toxicity, although their toxicity has not been investigated in detail. Terbium has no known biological role.
See also
Footnotes
- ↑ The term "rare earth metals" (or "rare earth elements") is a trivial name applied to 16 chemical elements: scandium, yttrium, and 14 of the 15 lanthanides (excluding promethium), which occur naturally on Earth. Some definitions also include the actinides. The word "earth" is an obsolete term for oxide. The term "rare earth" is discouraged by the International Union of Pure and Applied Chemistry (IUPAC), as these elements are relatively abundant in the Earth's crust.
ReferencesISBN links support NWE through referral fees
- Terbium Los Alamos National Laboratory, Chemistry Division. Retrieved February 22, 2007.
- Chang, Raymond (2006). Chemistry (ninth ed.) New York, NY: McGraw-Hill Science/Engineering/Math. ISBN 0073221031.
- Cotton, F. Albert; and Wilkinson, Geoffrey (1980). Advanced Inorganic Chemistry (4th ed.), New York, NY: Wiley. ISBN 0-471-02775-8.
- Greenwood, N.N.; and Earnshaw, A. (1998). Chemistry of the Elements (2nd Edition). Oxford, UK; Burlington, Massachusetts: Butterworth-Heinemann, Elsevier Science. ISBN 0750633654. Online version.
- Jones, Adrian P., Frances Wall, and C. Terry Williams (editors) (1996). Rare Earth Minerals: Chemistry, Origin and Ore Deposits (The Mineralogical Society Series). London, UK: Chapman and Hall. ISBN 0412610302 (ISBN-13: 978-0412610301).
- Stwertka, Albert (1998). Guide to the Elements, Revised Edition. Oxford, UK: Oxford University Press. ISBN 0-19-508083-1.
External links
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