Thulium

Thulium, ₆₉Tm
Thulium
Pronunciation	/ˈθjuːliəm/ ⓘ (THEW-lee-əm)
Appearance	silvery gray
Standard atomic weight Ar°(Tm)
	168.934219±0.000005; 168.93±0.01 (abridged);
Thulium in the periodic table
	erbium ← thulium → ytterbium
Atomic number (Z)	69
Group	f-block groups (no number)
Period	period 6
Block	f-block
Electron configuration	[Xe] 4f13 6s2
Electrons per shell	2, 8, 18, 31, 8, 2
Physical properties
Phase at STP	solid
Melting point	1818 K (1545 °C, 2813 °F)
Boiling point	2223 K (1950 °C, 3542 °F)
Density (at 20° C)	9.320 g/cm3
when liquid (at m.p.)	8.56 g/cm3
Heat of fusion	16.84 kJ/mol
Heat of vaporization	191 kJ/mol
Molar heat capacity	27.03 J/(mol·K)
Atomic properties
Oxidation states	common: +3; 0, +1, +2
Electronegativity	Pauling scale: 1.25
Ionization energies	1st: 596.7 kJ/mol ; 2nd: 1160 kJ/mol ; 3rd: 2285 kJ/mol ; ;
Atomic radius	empirical: 176 pm
Covalent radius	190±10 pm
	Spectral lines of thulium
Other properties
Natural occurrence	primordial
Crystal structure	hexagonal close-packed (hcp) (hP2)
Lattice constants	a = 353.77 pm; c = 555.39 pm (at 20 °C)
Thermal expansion	poly: 13.3 µm/(m⋅K) (at r.t.)
Thermal conductivity	16.9 W/(m⋅K)
Electrical resistivity	poly: 676 nΩ⋅m (at r.t.)
Magnetic ordering	paramagnetic (at 300 K)
Molar magnetic susceptibility	+25500×10−6 cm3/mol (291 K)
Young's modulus	74.0 GPa
Shear modulus	30.5 GPa
Bulk modulus	44.5 GPa
Poisson ratio	0.213
Vickers hardness	470–650 MPa
Brinell hardness	470–900 MPa
CAS Number	7440-30-4
History
Naming	after Thule, a mythical region in Scandinavia
Discovery	Per Teodor Cleve (1879)
First isolation	Wilhelm Klemm and Heinrich Bommer (1936)
Isotopes of thulium

Thulium is a chemical element; it has symbol Tm and atomic number 69. It is the thirteenth element in the lanthanide series of metals. It is the second-least abundant lanthanide in the Earth's crust, after radioactively unstable promethium. It is an easily workable metal with a bright silvery-gray luster. It is fairly soft and slowly tarnishes in air. Despite its high price and rarity, thulium is used as a dopant in solid-state lasers, and as the radiation source in some portable X-ray devices. It has no significant biological role and is not particularly toxic.

In 1879, the Swedish chemist Per Teodor Cleve separated two previously unknown components, which he called holmia and thulia, from the rare-earth mineral erbia; these were the oxides of holmium and thulium, respectively. His example of thulium oxide contained impurities of ytterbium oxide. A relatively pure sample of thulium oxide was first obtained in 1911. The metal itself was first obtained in 1936 by Wilhelm Klemm and Heinrich Bommer.^[9]

Like the other lanthanides, its most common oxidation state is +3, seen in its oxide, halides and other compounds. In aqueous solution, like compounds of other late lanthanides, soluble thulium compounds form coordination complexes with nine water molecules.

^ "Standard Atomic Weights: Thulium". CIAAW. 2021.
^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
^ ^a ^b Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
^ Yttrium and all lanthanides except Ce and Pm have been observed in the oxidation state 0 in bis(1,3,5-tri-t-butylbenzene) complexes, see Cloke, F. Geoffrey N. (1993). "Zero Oxidation State Compounds of Scandium, Yttrium, and the Lanthanides". Chem. Soc. Rev. 22: 17–24. doi:10.1039/CS9932200017. and Arnold, Polly L.; Petrukhina, Marina A.; Bochenkov, Vladimir E.; Shabatina, Tatyana I.; Zagorskii, Vyacheslav V.; Cloke (2003-12-15). "Arene complexation of Sm, Eu, Tm and Yb atoms: a variable temperature spectroscopic investigation". Journal of Organometallic Chemistry. 688 (1–2): 49–55. doi:10.1016/j.jorganchem.2003.08.028.
^ La(I), Pr(I), Tb(I), Tm(I), and Yb(I) have been observed in MB₈⁻ clusters; see Li, Wan-Lu; Chen, Teng-Teng; Chen, Wei-Jia; Li, Jun; Wang, Lai-Sheng (2021). "Monovalent lanthanide(I) in borozene complexes". Nature Communications. 12 (1): 6467. Bibcode:2021NatCo..12.6467L. doi:10.1038/s41467-021-26785-9. PMC 8578558. PMID 34753931.
^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. doi:10.1016/C2009-0-30414-6. ISBN 978-0-08-037941-8.
^ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
^ W. Klemm; H. Bommer (1937). "Zur Kenntnis der Metalle der seltenen Erden". Zeitschrift für anorganische und allgemeine Chemie (in German). 231 (1–2): 138–171. Bibcode:1937ZAACh.231..138K. doi:10.1002/zaac.19372310115..

[CIAAWthulium-1] "Standard Atomic Weights: Thulium". CIAAW. 2021.

[CIAAW2021-2] Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.

[Arblaster_2018-3] Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.

[Cloke1993-4] Yttrium and all lanthanides except Ce and Pm have been observed in the oxidation state 0 in bis(1,3,5-tri-t-butylbenzene) complexes, see Cloke, F. Geoffrey N. (1993). "Zero Oxidation State Compounds of Scandium, Yttrium, and the Lanthanides". Chem. Soc. Rev. 22: 17–24. doi:10.1039/CS9932200017. and Arnold, Polly L.; Petrukhina, Marina A.; Bochenkov, Vladimir E.; Shabatina, Tatyana I.; Zagorskii, Vyacheslav V.; Cloke (2003-12-15). "Arene complexation of Sm, Eu, Tm and Yb atoms: a variable temperature spectroscopic investigation". Journal of Organometallic Chemistry. 688 (1–2): 49–55. doi:10.1016/j.jorganchem.2003.08.028.

[LnI-5] La(I), Pr(I), Tb(I), Tm(I), and Yb(I) have been observed in MB₈⁻ clusters; see Li, Wan-Lu; Chen, Teng-Teng; Chen, Wei-Jia; Li, Jun; Wang, Lai-Sheng (2021). "Monovalent lanthanide(I) in borozene complexes". Nature Communications. 12 (1): 6467. Bibcode:2021NatCo..12.6467L. doi:10.1038/s41467-021-26785-9. PMC 8578558. PMID 34753931.

[GE28-6] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. doi:10.1016/C2009-0-30414-6. ISBN 978-0-08-037941-8.

[7] Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.

[NUBASE2020-8] Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.

[9] W. Klemm; H. Bommer (1937). "Zur Kenntnis der Metalle der seltenen Erden". Zeitschrift für anorganische und allgemeine Chemie (in German). 231 (1–2): 138–171. Bibcode:1937ZAACh.231..138K. doi:10.1002/zaac.19372310115..

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