Terbium

65

gadolinium ← terbium → dysprosium


-
↑
Tb
↓
Bk




periodic table




General


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)




Vapor pressure


P/Pa
1
10
100
1 k
10 k
100 k


at T/K
1789
1979
(2201)
(2505)
(2913)
(3491)



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




Main article: Isotopes of terbium


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%

Tb is stable with 94 neutrons


Terbium (chemical symbol Tb, atomic number 65) is a silvery-white rare earth metal.[1]

Contents

1 Occurrence
2 History
3 Notable characteristics

3.1 Isotopes


4 Compounds
5 Applications
6 Precautions
7 See also
8 Notes
9 References
10 External links
11 Credits



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 percent of terbium), xenotime (YPO4) and euxenite ((Y,Ca,Er,La,Ce,U,Th)(Nb,Ta,Ti)2O6, which contains one percent 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 six 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 one 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:

Fluorides
TbF3
TbF4
Chlorides
TbCl3
Bromides
TbBr3
Iodides
TbI3
Oxides
Tb2O3
Tb4O7
Sulfides
Tb2S3
Nitrides
TbN
See also terbium compounds.

Applications
Terbium is used to dope calcium fluoride, calcium tungstate, and strontium molybdate, which are used in solid-state devices. Also, sodium terbium borate is used in solid state devices.
Terbium is a crystal stabilizer of fuel cells that operate at elevated temperatures, together with zirconium(IV) oxide (ZrO2).
Terbium is used in alloys for the production of electronic devices.
Its oxide is used in green phosphors in fluorescent lamps and color TV tubes.
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
Chemical element
Inner transition metal
Metal
Periodic table
Notes

↑ 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
Chang, Raymond. Chemistry. 9th ed. New York: McGraw-Hill Science/Engineering/Math, 2006. ISBN 0073221031
Cotton, F. Albert, and Geoffrey Wilkinson. Advanced Inorganic Chemistry. 4th ed. New York: Wiley, 1980. ISBN 0-471-02775-8
Greenwood, N.N. and A. Earnshaw. Chemistry of the Elements. 2nd ed. Oxford, U.K.; Burlington, MA: Butterworth-Heinemann, Elsevier Science, 1998. ISBN 0750633654 Online version Retrieved September 17, 2007.
Jones, Adrian P., Frances Wall, and C. Terry Williams, eds. Rare Earth Minerals: Chemistry, Origin and Ore Deposits. The Mineralogical Society Series. London, UK: Chapman and Hall, 1996. ISBN 0412610302
Stwertka, Albert. Guide to the Elements. Rev. ed. Oxford, UK: Oxford University Press, 1998. ISBN 0-19-508083-1
"Terbium" Los Alamos National Laboratory, Chemistry Division, 2003. Retrieved September 17, 2007.
External links
All links retrieved January 23, 2020.

WebElements.com – Terbium
It's Elemental – Terbium

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