Thulium

Metal

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

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Electronic 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

Thermal data

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

Steric data

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

Nuclide	Abundance [%]	Mass	Spin	Halflife	Decay mode	Decay 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

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.

Thulium

Physical data

Electronic data

Thermal data

Steric data

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