Thulium

69

erbium ← thulium → ytterbium


-
↑
Tm
↓
Md




periodic table




General


Name, Symbol, Number

thulium, Tm, 69


Chemical series
lanthanides


Group, Period, Block

n/a, 6, f


Appearance
silvery gray 



Atomic mass
168.93421(2) g/mol


Electron configuration
[Xe] 4f13 6s2


Electrons per shell
2, 8, 18, 31, 8, 2


Physical properties


Phase
solid


Density (near r.t.)
9.32 g/cm³


Liquid density at m.p.
8.56 g/cm³


Melting point
1818 K
(1545 °C, 2813 °F)


Boiling point
2223 K
(1950 °C, 3542 °F)


Heat of fusion
16.84 kJ/mol


Heat of vaporization
247 kJ/mol


Heat capacity
(25 °C) 27.03 J/(mol·K)




Vapor pressure


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


at T/K
1117
1235
1381
1570
(1821)
(2217)



Atomic properties


Crystal structure
hexagonal


Oxidation states
3
(basic oxide)


Electronegativity
1.25 (Pauling scale)


Ionization energies
(more)

1st: 596.7 kJ/mol


2nd: 1160 kJ/mol


3rd: 2285 kJ/mol


Atomic radius
175 pm


Atomic radius (calc.)
222 pm


Miscellaneous


Magnetic ordering
no data


Electrical resistivity
(r.t.) (poly) 676 nΩ·m


Thermal conductivity
(300 K) 16.9 W/(m·K)


Thermal expansion
(r.t.) (poly)
13.3 µm/(m·K)


Speed of sound (thin rod)
(r.t.) 74.0 m/s


Shear modulus
30.5 GPa


Bulk modulus
44.5 GPa


Poisson ratio
0.213


Vickers hardness
520 MPa


Brinell hardness
471 MPa


CAS registry number
7440-30-4


Notable isotopes




Main article: Isotopes of thulium


iso

NA

half-life

DM

DE (MeV)

DP


167Tm

syn

9.25 d

ε

0.748

167Er


168Tm

syn

93.1 d

ε

1.679

168Er


169Tm

100%

Tm is stable with 100 neutrons


170Tm

syn

128.6 d

β-

0.968

170Yb


171Tm

syn

1.92 y

β-

0.096

171Yb


Thulium (chemical symbol Tm, atomic number 69) is the least abundant of the rare earth metals.[1] It has a bright, silvery-gray luster.

Contents

1 Occurrence
2 History
3 Notable characteristics

3.1 Isotopes


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



Occurrence
The element is never found in nature in pure form, but it is found in small quantities in minerals with other rare earths. It is principally extracted from monazite (~0.007 percent thulium) ores found in river sands through ion-exchange. Newer ion-exchange and solvent extraction techniques have led to easier separation of the rare earths, which has yielded much lower costs for thulium production. The metal can be isolated through reduction of its oxide with lanthanum metal or by calcium reduction in a closed container. None of thulium's compounds are commercially important.

History
Thulium was discovered by Swedish chemist Per Teodor Cleve in 1879 by looking for impurities in the oxides of other rare earth elements (this was the same method Carl Gustaf Mosander earlier used to discover some other rare earth elements). Cleve started by removing all of the known contaminants of erbia (Er2O3) and upon additional processing, obtained two new substances; one brown and one green. The brown substance turned out to be the oxide of the element holmium and was named holmia by Cleve and the green substance was the oxide of an unknown element. Cleve named the oxide thulia and its element thulium after Thule, Scandinavia.

Notable characteristics
Thulium is an inner transition metal (or lanthanide) that lies in period six of the periodic table, between erbium and ytterbium. It is easy to work and can be cut by a knife. It is ductile and is somewhat resistant to corrosion in dry air.

Isotopes
Naturally occurring thulium is composed of a single stable isotope, Tm-169 (100 percent natural abundance). 31 radioisotopes have been characterized, with the most stable being Tm-171 with a half-life of 1.92 years, Tm-170 with a half-life of 128.6 days, Tm-168 with a half-life of 93.1 days, and Tm-167 with a half-life of 9.25 days. All of the remaining radioactive isotopes have half-lives that are less than 64 hours, and the majority of these have half lives that are less than two minutes. This element also has 14 meta states, with the most stable being Tm-164m (t½ 5.1 minutes), Tm-160m (t½ 74.5 seconds), and Tm-155m (t½ 45 seconds).
The isotopes of thulium range in atomic weight from 145.966 u (Tm-146) to 176.949 u (Tm-177). The primary decay mode before the most abundant stable isotope, Tm-169, is electron capture, and the primary mode after is beta emission. The primary decay products before Tm-169 are element 68 (erbium) isotopes, and the primary products after are element 70 (ytterbium) isotopes.

Applications
Thulium has been used to create lasers, but high production costs have prevented other commercial uses from being developed. Other applications, real and potential, include:

When stable thulium (Tm-169) is bombarded in a nuclear reactor, it can later serve as a radiation source in portable X-ray devices.
The unstable isotope Tm-171 could possibly be used as an energy source.
Tm-169 has potential use in ceramic magnetic materials called ferrites, which are used in microwave equipment.
Precautions
Thulium has a low-to-moderate acute toxic rating and should be handled with care. Metallic thulium in dust form presents a fire and explosion hazard.

See also
Chemical element
Inner transition metal
Metal
Periodic table
Thulium compounds.
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 20, 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
"Thulium" Los Alamos National Laboratory, Chemistry Division. Retrieved September 20, 2007.
"Thulium" It's Elemental. Jefferson Lab. Retrieved September 20, 2007.
External links
All links retrieved March 12, 2020.

Thulium WebElements.com.

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