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Atomic Number	81

Atomic Symbol	Tl

Atomic Weight	204.3833 amu

Group	Other Metals, 13

Form	Solid

Density @ STP	11.8 g/cm³

Melting Point	304 °C (579.2 °F, 577.15 °K)

Boiling Point	1473 °C (2683.4 °F, 1746.15 °K)

Heat of Fusion	4.14 kJ/mol

Heat of Vaporization	165 kJ/mol

First Ionization Potential	6.10829 eV

Electronegativity (on Pauling scale	1.8

Specific Heat Capacity	0.129 J/g K

Ground State Electron Configuration	5d¹⁰ 6s² 6p¹

Oxidation State(s)	+1, +3

Stable Isotopes and Natural Abundance on Earth	²⁰³Tl, 29.524%; ²⁰⁵Tl, 70.476%

Selected Radioisotopes	²⁰¹Tl

Atomic Radius	156 pm

Crystal Structure	Hexagonal

Discovered by	Crookes, 1861