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Thulium

Metalsolid
Symbol: Tm
Atomic number: 69
Atomic mass: 168.93421
Group: Lanthanide
CAS-number: 7440-30-4

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Physical data
Isotopes
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Physical data

Electronic dataThermal dataSteric data
Shells: 2, 8, 18, 31, 8, 2
Orbitals: [Xe] 4f13 6s2
Electronegativity: --, 1.1
1. Ionization potential: 6.1843 eV
2. Ionization potential: 12.054 eV
3. Ionization potential: 26.367 eV
Oxidation states: 3, 2
Electrical conductivity: 0.0150 10^6
Melting point: 1545 °C
Boiling point: 1950 °C
Specific heat: 0.16 J/gK
Heat of fusion: 16.840 kJ/mol
Heat of vaporization: 191.0 kJ/mol
Thermal conductivity: 0.168 W/cmK
Atomic radius: 2.42 Å
Ionic radius: 1.09 Å (+3)
Covalent radius: 1.56 Å
Atomic volume: 18.1 cm³/mol
Density (293 K): 9.33 g/cm³
Crystal structure: hexagonal
hexagonal

Isotopes

NuclideAbundance [%]MassSpinHalflifeDecay modeDecay tree
168Tm 0 168 3 93.1d EC View
169Tm 100 168.934 1/2 -- --
170Tm 0 170 1 128.6d β- View
171Tm 0 171 1/2 1.92y β- View
172Tm 0 172 2 2.65d β- View

Other info

Name origin:From Thule ancient name of Scandinavia.
Description:Soft, malleable, ductile, silvery metal
Discovered by:Per Theodor Cleve
Year:1879
Place:Sweden
Sources:Found with other rare earths in the minerals gadolinite, euxenite, xenotime, and monazite. Monazite is often 50% rare earth by mass and 0.007% thulium.
Use(s):Radioactive thulium is used to power portable x-ray machines, eliminating the need for electrical equipment.