Terbium
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| General | ||||||||||||||||||||||||||||
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| Name, Symbol, Number | Terbium, Tb, 65 | |||||||||||||||||||||||||||
| Chemical series | Lanthanides | |||||||||||||||||||||||||||
| Group, Period, Block | _ , 6 , f | |||||||||||||||||||||||||||
| Density, Hardness | 8219 kg/m3, no data | |||||||||||||||||||||||||||
| Appearance | silvery white | |||||||||||||||||||||||||||
| Atomic properties | ||||||||||||||||||||||||||||
| Atomic weight | 158.92534(2) amu | |||||||||||||||||||||||||||
| Atomic radius (calc.) | 175 (225) pm | |||||||||||||||||||||||||||
| Covalent radius | no data | |||||||||||||||||||||||||||
| van der Waals radius | no data | |||||||||||||||||||||||||||
| Electron configuration | [Xe]6s²4f9 | |||||||||||||||||||||||||||
| e- 's per energy level | 2, 8, 18, 27, 8, 2 | |||||||||||||||||||||||||||
| Oxidation states (Oxide) | 4 (weak base) | |||||||||||||||||||||||||||
| Crystal structure | Hexagonal | |||||||||||||||||||||||||||
| Physical properties | ||||||||||||||||||||||||||||
| State of matter | solid (__) | |||||||||||||||||||||||||||
| Melting point | 1629 K (2473 °F) | |||||||||||||||||||||||||||
| Boiling point | 3503 K (5846 °F) | |||||||||||||||||||||||||||
| Molar volume | 19.3 ×10-3 m3/mol | |||||||||||||||||||||||||||
| Heat of vaporization | 330.9 kJ/mol | |||||||||||||||||||||||||||
| Heat of fusion | 10.8 kJ/mol | |||||||||||||||||||||||||||
| Vapor pressure | no data | |||||||||||||||||||||||||||
| Velocity of sound | 2620 m/s at 293.15 K | |||||||||||||||||||||||||||
| Miscellaneous | ||||||||||||||||||||||||||||
| Electronegativity | 1.2 (Pauling scale) | |||||||||||||||||||||||||||
| Specific heat capacity | 180 J/(kg*K) | |||||||||||||||||||||||||||
| Electrical conductivity | 0.889 106/m ohm | |||||||||||||||||||||||||||
| Thermal conductivity | 11.1 W/(m*K) | |||||||||||||||||||||||||||
| 1st ionization potential | 565.8 kJ/mol | |||||||||||||||||||||||||||
| 2nd ionization potential | 1110 kJ/mol | |||||||||||||||||||||||||||
| 3rd ionization potential | 2114 kJ/mol | |||||||||||||||||||||||||||
| 4th ionization potential | 3839 kJ/mol | |||||||||||||||||||||||||||
| Most stable isotopes | ||||||||||||||||||||||||||||
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| SI units & STP are used except where noted. | ||||||||||||||||||||||||||||
Terbium is a chemical element in the periodic table that has the symbol Tb and atomic number 65.
Notable characteristics
Terbium is a silvery-gray rare earth metal that is malleable, ductile and soft enough to be cut with a knife. It is reasonably stable in air, and two crystal modifications exist, with a transformation temperature of 1289°C.
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, and its oxide has potential as an activator for green phosphors used in colour TV tubes. Sodium Terbium borate is used as a laser material that emits coherent light at 5460 Å.
History
Terbium was discovered by Swedish chemist Carl Gustaf Mosander in 1843 and named after the village Ytterby in Sweden, who detected it as an impurity in Yttrium-oxide, Y2O3. It was not isolated in pure form until the recent advent of ion-exchange techniques.
Biological role
Terbium has no known biological role.
Occurrence
Terbium is never found in nature as the free element, but it is contained in many minerals, including cerite, gadolinite, monazite (Ce,LaTh,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).
Compounds
Terbium compounds include:
Isotopes
Naturally occurring Terbium is composed of 1 stable isotope, 159-Tb. 33 radioisotopes have been characterized, with the most 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.
Precautions
All terbium compounds should be regarded as highly toxic. Terbium compounds are skin and eye irritants. The metal dust presents a fire and explosion hazard.