Electronic data		Thermal data		Steric 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 () 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	--	stable	--
170Tm	0	170	1	128.6d	-	View
171Tm	0	171	1/2	1.92y	-	View
172Tm	0	172	2	2.65d	-	View

Legend

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 weight and 0.007% thulium.
Use(s):	Radioactive thulium is used to power portable x-ray machines, eliminating the need for electrical equipment.