Thulium

Thulium - Tm

CAS: 7440-30-4
Description: Silver-gray, soft, malleable, ductile metal
Classification: Rare Earth (Lanthanide)
Date of Discovery: 1879
Discoverer: Per Theodor Cleve
Name Origin: Thule, earliest name for Scandinavia

Atomic Number: 69
Number of Neutrons: 100
Atomic Mass: 168.93421(3) amu
Melting Point: 1545 °C
Boiling Point: 1950 °C
Density (25 °C): 9.321 g/cm³
Atomic volume: 18.1 cm³/mol
Electrical resistivity: 0.0150 10^-6/cm

Thermal conductivity: 0.168 W/cmK
Enthalpy of atomization: 247 kJ/mol (est.)
Enthalpy of vaporization: 191.0 kJ/mol
Enthalpy of fusion: 16.840 kJ/mol
Specific heat capacity: 0.16 J/gK

Energy levels: 2-8-18-31-8-2
Electron configuration: [Xe]4f ¹³6s²
Crystal Structure: Hexagonal
Atomic radius: 2.42 Å
Covalent radius: 1.56 Å
Oxidation States: +2(?) and +3
Electronegativity, Pauling: 1.24
Electron affinity:
First ionization energy: 6.184 eV
2nd ionization energy: 12.054 eV
3rd ionization energy: 26.367 eV
Polarizability: 21.8 10^-24cm³

Isotope	Natural Abundance	Atomic Mass	Half-life	Decay Mode	Spin
¹⁴⁶Tm	145.967	⁺; p
¹⁴⁷Tm	146.961	0.6 s	EC, ⁺; p
¹⁴⁸Tm	147.9573	0.7 s	⁺, EC
¹⁴⁹Tm	148.9524	0.9 s	⁺, EC	11/2-
¹⁵⁰Tm	149.9494	2.3	⁺, EC	6-
¹⁵¹Tm	150.9454	4 s	⁺, EC
^152mTm	8 s	⁺, EC	9+
¹⁵²Tm	151.9443	5 s	⁺, EC
¹⁵³Tm	152.94203	1.6 s	⁺;
^154mTm	3.3 s	⁺;
¹⁵⁴Tm	153.9407	8.1 s	⁺;	9+
¹⁵⁵Tm	154.93919	30 s	⁺;
^156mTm	19 s
¹⁵⁶Tm	155.9389	1.40 m	⁺;	2-
¹⁵⁷Tm	156.9367	3.6 m	⁺;	1/2
¹⁵⁸Tm	157.9379	4.0 m	⁺; EC	(2-)
¹⁵⁹Tm	158.9348	9.1 m	⁺; EC	5/2+
^160mTm	1.24 m	IT	(5)
¹⁶⁰Tm	159.9354	9.4 m	⁺; EC	1-
¹⁶¹Tm	160.9334	31 m	⁺, EC	7/2+
^162mTm	24 s	IT; ⁺, EC	5+
¹⁶²Tm	161.93394	21.7 m	⁺; EC	1-
¹⁶³Tm	162.93265	1.81 h	EC; ⁺
^164mTm	5.1 m	IT; ⁺, EC	6-
¹⁶⁴Tm	163.93345	2.0 m	⁺; EC	1+
¹⁶⁵Tm	164.932433	1.253 d	EC	1/2+
¹⁶⁶Tm	165.93355	7.70 h	EC; ⁺
¹⁶⁷Tm	166.932849	9.24 d	EC	1/2+
¹⁶⁸Tm	167.934171	93.1 d	EC	3+
¹⁶⁹Tm	100.	168.934211	Stable	1/2+
¹⁷⁰Tm	169.935798	128.6 d	^-; EC	1-
¹⁷¹Tm	170.936426	1.92 y	^-	1/2+
¹⁷²Tm	171.93840	2.65 d	^-	2-
¹⁷³Tm	172.93960	8.2 h	^-	1/2+
¹⁷⁴Tm	173.94216	5.4 m	^-	(4-)
¹⁷⁵Tm	174.94383	15.2 m	^-	(1/2+)
¹⁷⁶Tm	175.9471	1.9 m	^-	(4+)
Discovered in 1879 by Cleve. Thulium occurs in small quantities along with other rare earths in a number of minerals. It is obtained commercially from monazite, which contains about 0.007% of the element. Thulium is the least abundant of the rare earth elements, but with new sources recently discovered, it is now considered to be about as rare as silver, gold, or cadmium. Ion-exchange and solvent extraction techniques have recently permitted much easier separation of the rare earths, with much lower costs. Thulium can be isolated by reduction of the oxide with lanthanum metal or by calcium reduction of the anhydrous fluoride. The pure metal has a bright, silvery luster. It is reasonably stable in air, but the metal should be protected from moisture in a closed container. The element is silver-gray, soft, malleable, and ductile, and can be cut with a knife. Thirty-eight isotopes and isomers are known, with atomic masses ranging from 146 to 176. Natural thulium, which is 100% ¹⁶⁹Tm, is stable. Because of the relatively high price of the metal, thulium has not yet found many practical applications. ¹⁶⁹Tm bombarded in a nuclear reactor can be used as a radiation source in portable X-ray equipment. ¹⁷¹Tm is potentially useful as an energy source. Natural thulium also has possible use in ferrites (ceramic magnetic materials) used in microwave equipment. As with other lanthanides, thulium has a low-to-moderate acute toxic rating. It should be handled with care. LINKS: Information, data sheet and standard forms Oak Ridge Physicists Discover New Proton-Emitting Thulium Isotope Return Sources for the information on this website include: Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998.

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