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Atomic Number	69

Atomic Symbol	Tm

Atomic Weight	168.93421 amu

Group	Rare Earth (Lanthanide Series)

Form	Solid

Density @ STP	9.32 g/cm³

Melting Point	1545 °C (2843 °F, 1818.15 °K)

Boiling Point	1950 °C (3542 °F, 2223.15 °K)

Heat of Fusion	16.84 kJ/mol

Heat of Vaporization	250 kJ/mol

First Ionization Potential	6.18431 eV

Electronegativity (on Pauling scale	1.25

Specific Heat Capacity	0.129 J/g K

Ground State Electron Configuration	4f¹³ 5s² 5p⁶ 6s²

Oxidation State(s)	+3

Stable Isotopes and Natural Abundance on Earth	¹⁶⁹Tm, 100%

Selected Radioisotopes	¹⁷⁰Tm, ¹⁷¹Tm

Atomic Radius	222 pm

Crystal Structure	Hexagonal

Discovered by	Cleve, 1879