Terbium

Terbium is a chemical element; it has symbol Tb and atomic number 65. It is a silvery-white, rare earth metal that is malleable, and ductile. The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with water, evolving hydrogen gas. Terbium is never found in nature as a free element, but it is contained in many minerals, including cerite, gadolinite, monazite, xenotime and euxenite.

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Terbium, ₆₅Tb

Terbium
Pronunciation	/ˈtɜːrbiəm/ ​(TUR-bee-əm)
Appearance	silvery white
Standard atomic weight Ar°(Tb)
	158.925354±0.000007 158.93±0.01 (abridged)[1]
Terbium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson – ↑ Tb ↓ Bk gadolinium ← terbium → dysprosium
Atomic number (Z)	65
Group	f-block groups (no number)
Period	period 6
Block	f-block
Electron configuration	[Xe] 4f9 6s2
Electrons per shell	2, 8, 18, 27, 8, 2
Physical properties
Phase at STP	solid
Melting point	1629 K ​(1356 °C, ​2473 °F)
Boiling point	3396 K ​(3123 °C, ​5653 °F)
Density (near r.t.)	8.23 g/cm3
when liquid (at m.p.)	7.65 g/cm3
Heat of fusion	10.15 kJ/mol
Heat of vaporization	391 kJ/mol
Molar heat capacity	28.91 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 1789 1979 (2201) (2505) (2913) (3491)
Atomic properties
Oxidation states	0,[2] +1,[3] +2, +3, +4 (a weakly basic oxide)
Electronegativity	Pauling scale: 1.2 (?)
Ionization energies	1st: 565.8 kJ/mol 2nd: 1110 kJ/mol 3rd: 2114 kJ/mol
Atomic radius	empirical: 177 pm
Covalent radius	194±5 pm
Spectral lines of terbium
Other properties
Natural occurrence	primordial
Crystal structure	​hexagonal close-packed (hcp)
Speed of sound thin rod	2620 m/s (at 20 °C)
Thermal expansion	at r.t. α, poly: 10.3 µm/(m⋅K)
Thermal conductivity	11.1 W/(m⋅K)
Electrical resistivity	α, poly: 1.150 µΩ⋅m (at r.t.)
Magnetic ordering	paramagnetic at 300 K
Molar magnetic susceptibility	+146000×10−6 cm3/mol (273 K)[4]
Young's modulus	α form: 55.7 GPa
Shear modulus	α form: 22.1 GPa
Bulk modulus	α form: 38.7 GPa
Poisson ratio	α form: 0.261
Vickers hardness	450–865 MPa
Brinell hardness	675–1200 MPa
CAS Number	7440-27-9
History
Naming	after Ytterby (Sweden), where it was mined
Discovery and first isolation	Carl Gustaf Mosander (1843)
Isotopes of terbium v e
Main isotopes[5] Decay abun­dance half-life (t1/2) mode pro­duct 157Tb synth 71 y ε 157Gd 158Tb synth 180 y ε 158Gd β− 158Dy 159Tb 100% stable
Category: Terbium view talk edit | references

Swedish chemist Carl Gustaf Mosander discovered terbium as a chemical element in 1843. He detected it as an impurity in yttrium oxide, Y₂O₃. Yttrium and terbium, as well as erbium and ytterbium, are named after the village of Ytterby in Sweden. Terbium was not isolated in pure form until the advent of ion exchange techniques.

Terbium is used to dope calcium fluoride, calcium tungstate and strontium molybdate in solid-state devices, and as a crystal stabilizer of fuel cells that operate at elevated temperatures. As a component of Terfenol-D (an alloy that expands and contracts when exposed to magnetic fields more than any other alloy), terbium is of use in actuators, in naval sonar systems and in sensors.

Most of the world's terbium supply is used in green phosphors. Terbium oxide is used in fluorescent lamps and television and monitor cathode-ray tubes (CRTs). Terbium green phosphors are combined with divalent europium blue phosphors and trivalent europium red phosphors to provide trichromatic lighting technology, a high-efficiency white light used for standard illumination in indoor lighting.