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Gadolinium - Terbium - Dysprosium
Name, Symbol, NumberTerbium, 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]6s6s²4f9
e- 's per energy level2, 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 ×1010-3 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
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
isoNAhalf-life DMDE MeVDP
157Tb{syn.}71 a &epsilon0.060157Gd
158Tb{syn.}180 aε1.220158Gd
159Tb100%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.

Table of contents
1 Notable characteristics
2 Applications
3 History
4 Biological role
5 Occurrence
6 Compounds
7 Isotopes
8 Precautions
9 External links

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 1289C.


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.


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.


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).


Terbium compounds include:


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 (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.


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.

External links