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Terbium

From Academic Kids

GadoliniumTerbiumDysprosium
Tb
Bk  
 
 
Image:Tb-TableImage.png
General
Name, Symbol, Number Terbium, Tb, 65
Chemical series Lanthanides
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 (Ferromagnetic
in dry ice [1] (http://www.irm.umn.edu/quarterly/irmq10-3.pdf))
Melting point 1629 K (2473 ?F)
Boiling point 3503 K (5846 ?F)
Molar volume 19.3 ×10-6 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
iso NA half-life DM DE MeV DP
157Tb {syn.} 71 y ε 0.060 157Gd
158Tb {syn.} 180 y ε 1.220 158Gd
β- 0.937 158Dy
159Tb 100% 159Tb is stable with 94 neutrons
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.

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Contents

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, its oxide is used in green phosphors in fluorescent lamps and color TV tubes. Sodium terbium borate is used as a laser material that emits coherent light at 546 nm.

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.

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 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 (t? 24.4 hours), 154m2-Tb (t? 22.7 hours) and 154m1-Tb (t? 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

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.

References

External links

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