Electronic data		Thermal data		Steric data
Shells: 2,8,18,32,18,3 Orbitals: [Xe] 4f14 5d10 6s2 6p1 Electronegativity: 1.4, 1.8 1. Ionization potential: 6.1083 eV 2. Ionization potential: 20.428 eV 3. Ionization potential: 29.829 eV Oxidation states: 3,1 Electrical conductivity: 0.0617 10^6		Melting point: 303.5 °C Boiling point: 1457 °C ±10 Specific heat: 0.13 J/gK Heat of fusion: 4.142 kJ/mol Heat of vaporization: 164.10 kJ/mol Thermal conductivity: 0.461 W/cmK		Atomic radius: 2.08 Å Ionic radius: 1.59 Å () Covalent radius: 1.48 Å Atomic volume: 17.2 cm³/mol Density (293 K): 11.85 g/cm³ Crystal structure: Hexagonal

Nuclide	Abundance [%]	Mass	Spin	Halflife	Decay mode	Decay tree
200Tl	0	200	2	1.087d	EC,+	View
201Tl	0	201	1/2	3.038d	EC	View
202Tl	0	202	2	12.23d	EC,+	View
203Tl	29.52	202.972	1/2	--	stable	--
204Tl	0	204	2	3.78y	-,EC	View
205Tl	70.48	204.974	1/2	--	stable	--
206Tl	0	206	0	4.20m	-	View
207Tl	0	207	0	4.77m	-	View
208Tl	0	208	0	3.053m	-	View
209Tl	0	209	1/2	2.20m	-	View
210Tl	0	210	0	1.30m	-	View

Legend

Name origin:	Greek: thallos (green twig), for a bright green line in its spectrum.
Description:	Soft gray metal that looks like lead.
Discovered by:	Sir William Crookes
Year:	1861
Place:	England
Sources:	Found in iron pyrites. Also in crookesite, hutchinsonite and lorandite. Most is recovered from the byproducts of lead and zinc refining.
Use(s):	Its compounds are used in rat and ant poisons. Also for detecting infrared radiation.