69
  Tm  
168.934210
Thulium

Name: Thulium
Symbol: Tm
Atomic Number: 69
Atomic Weight: 168.934210
Family: Rare Earth Elements
CAS RN: 7440-30-4
Description: A silvery-grey, soft, malleable, and ductile rare earth metal.
State (25C): Solid
Oxidation states: +3

Molar Volume: 18.12 cm3/mole
Valence Electrons: 4f136s2

Boiling Point:  2220K, 1947C, 3537F
Melting Point:
1818K, 1545C, 2813F
Electrons Energy Level: 2, 8, 18, 31, 8, 2
Isotopes: 34 + 1 Stable + 14 meta states
Heat of Vaporization:  191 kJ/mol
Heat of Fusion: 16.84 kJ/mol
Density:  9.32 g/cm3 @ 300K
Specific Heat:  0.16 J/gK
Atomic Radius: 2.42
Ionic Radius: 0.869
Electronegativity: 1.25 (Pauling); 1.11 (Allrod Rochow)
Vapor Pressure: 0.0049 Pa @ 1545C
57
La
138.9
58
Ce
140.1
59
Pr
140.9
60
Nd
144.2
61
Pm
(145)
62
Sm
150.4
63
Eu
152.0
64
Gd
157.3
65
Tb
158.9
66
Dy
162.5
67
Ho
164.9
68
Er
167.3
69
Tm
168.9
70
Yb
173.0
71
Lu
175.0

1s2 2s2p6 3s2p6d10 4s2p6d10f13 5s2p6 6s2

History

The rarest of the naturally-occurring rare-earth metals, thulium was discovered by Swedish chemist Per Teodor Cleve in 1879 by looking for impurities in samples of erbia, an oxide of erbium (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.   The green substance was the oxide of an unknown element.   Cleve named the oxide thulia and its element thulium for the ancient name for Scandinavia, Thule.

Characteristics

Like others in the lanthanide series, thulium is silver in color but it is also very soft---soft enough to cut with a knife.  Thulium is the least abundant of the naturally occurring rare earth elements. 

1s2
2s2 2p6
3s2 3p6 3d10
4s2 4p6 4d10 4f13
5s2 5p6
6s2

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% 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.

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:

Metallic thulium is relatively expensive and has only recently become available.  It currently has no commercial applications.

Compounds

Thulium forms no commercially important compounds.  Some of thulium's compounds include: thulium oxide (Tm2O3), thulium fluoride (TmF3) and thulium iodide (TmI3).

Isotopes

Naturally occurring thulium is composed of 1 stable isotope169Tm (100% natural abundance.  34 radioisotopes have been characterized, with the most stable being 171Tm with a half-life of 1.92 years, 170Tm with a half-life of 128.6 days, 168Tm with a half-life of 93.1 days, and 167Tm with a half-life of 9.25 days.  All of the remaining radioactive isotopes have half-lifes that are less than 64 hours, and the majority of these have half lifes that are less than 2 minutes.  This element also has 14 meta states, with the most stable being Tm-164m (t 5.1 minutes), Tm-160m (t 74.5 seconds) and Tm-155m (t 45 seconds).

The isotopes of thulium range in atomic weight from 144.97007 amu (145Tm) to 178.95534 amu (179Tm).  The primary decay mode before the most abundant stable isotope, 169Tm, is electron capture, and the primary mode after is beta emission.  The primary decay products before 169Tm are element erbium-68 isotopes, and the primary products after are element  ytterbium-70 isotopes.

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Isotope  
Atomic Mass
 
Half-Life
145Tm 144.97007 3.1 s
146Tm 145.96643 240 ms
147Tm 146.96096 0.58 seconds
148Tm 147.95784 0.7 seconds
149Tm 148.95272 0.9 seconds
150Tm 149.94996 ~3 seconds
150m1Tm   2.20 seconds
151Tm 150.945483 4.17 seconds
151m1Tm   6.6 seconds
152Tm 151.94442 8.0 seconds
152m1Tm   5.2 seconds
153Tm 152.942012 1.48 seconds
153mTm   2.5 seconds
154Tm 153.941568 8.1 seconds
154mTm   3.30 seconds
155Tm 154.939199 21.6 seconds
155mTm   45 seconds
156Tm 155.938980 83.8 seconds
157Tm 156.93697 3.63 minutes
158Tm 157.936980 3.98 minutes
159Tm 158.93498 9.13 minutes
160Tm 159.93526 9.4 minutes
160m1Tm   74.5 seconds
161Tm 160.93355 30.2 minutes
161m1Tm   ~5 minutes
162Tm 161.933995 21.70 minutes
162mTm   24.3(17) seconds
163Tm 162.932651 1.810 hours
164Tm 163.93356 2.0 minutes
164mTm   5.1 minutes
165Tm 164.932435 30.06 hours
166Tm 165.933554 7.70 hours
167Tm 166.9328516 9.25 days
168Tm 167.934173 93.1 days
169Tm 168.9342133 Stable
170Tm 169.9358014 128.6 days
171Tm 170.9364294 1.92 years
172Tm 171.938400 63.6 hours
173Tm 172.939604 8.24 hours
174Tm 173.94217 5.4 minutes
175Tm 174.94384 15.2 minutes
176Tm 175.94699 1.85 minutes
177Tm 176.94904 90 seconds
178Tm 177.95264 ~30 seconds
179Tm 178.95534 ~20 seconds

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.

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Thulium Data

 

Atomic Structure

Atomic Radius (): 2.42
Atomic Volume cm3/mol : 18.1cm3/mol
Covalent Radius: 1.56
Crystal Structure: Hexagonal
Ionic Radius: 0.869

Chemical Properties

Electrochemical Equivalents: 2.101g/amp-hr
Electron Work Function: unknown
Electronegativity: 1.25 (Pauling); 1.11 (Allrod Rochow)
Heat of Fusion: 16.84kJ/mol
First Ionization Potential: 6.184
Second Ionization Potential: 12.054
Third Ionization Potential: 26.367
Valence Electron Potential: 49.7 -eV
Ionization Energy (eV): 6.184 eV

Physical Properties

Atomic Mass Average: 168.9342
Boiling Point: 2220K, 1947C, 3537F
Melting Point: 1818K, 1545C, 2813F
Heat of Vaporization: 191 kJ/mol
Coefficient of Lineal Thermal Expansion/K-1: 13.3E-6
Electrical Conductivity: 0.015 106/cm
Thermal Conductivity: 0.168 W/cmK
Density: 9.32 g/cm3 @ 300K
Enthalpy of Atomization: 247 kJ/mole @ 25C
Enthalpy of Fusion: 16.8 kJ/mole
Enthalpy of Vaporization: 191 kJ/mole
Molar Volume: 18.12 cm3/mole
Specific Heat: 0.16 J/gK
Vapor Pressure: 0.0049 Pa @ 1545C
Estimated Crustal Abundance: 5.210-1 milligrams per kilogram
Estimated Oceanic Abundance: 1.710-7 milligrams per liter