thallium

• Description
• General information
• Physical data
• Radii
• Electronegativities
• Solid state structure
• Temperatures
• Enthalpies
• Ionization Enthalpies
• Isotopes
• Further information

Description

When freshly exposed to air, thallium exhibits a metallic lustre, but soon develops a bluish-grey tinge, resembling lead in appearance. A heavy oxide builds up on thallium if left in air, and in the presence of water the hydroxide is formed. The metal is very soft and malleable. It can be cut with a knife.

The element and its compounds are toxic and should be handled carefully. Thallium may cause cancer.

General information

Discoveror: Sir William Crookes
Date discovered: 1861
Discovered at: England
Meaning of name: From the Greek word "thallos" meaning "green twig" or green shoot

Physical data

Standard state: solid at 298 K
Colour: silvery white
Density of solid at ambient temperature/kg m^-3: 11850
Molar volume/cm³: 17.22

Radii /pm

Atomic: 156
Covalent (single bond):
Pauling radius for the ion [Tl]^-: no data

Valence shell orbital radius maxima (R_max)

orbital	s	p	d	f
radius	129.7	165.9	58.4	18.8

Electronegativities

Both values are quoted on the Pauling scale.

Pauling: 1.8
Allred Rochow: 1.44

Crystal Structure

structure: hcp (hexagonal close-packed)

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.

Temperatures (/K)

melting point: 577
boiling point: 1746

Enthalpies /kJ mol^-1

fusion: 4.2
vaporization: 164

single bond enthalpies:

Tl-F	Tl-Cl	Tl-Br	Tl-I	Tl-Tl
439	364	326	280	60.7

Ionization enthalpies /kJ mol^-1

Number	Enthalpy
1st	589.3
2nd	1971.0
3rd	2878

Isotopes

This section gives some data for naturally occurring isotopes.

Nominal mass	Accurate mass	% natural abundance
203Tl	202.972320 (5)	29.524 (14)
205Tl	204.974401 (5)	70.476 (14)

Further Information

• Additional information about WebElements 1.2.2
• This is a licensed copy (here is the full list) of WebElements 1.2.2 and contains a subset of the material contained within the main version of WebElements (version 2)
• For further information please try WebElements version 2
• Sheffield Chemdex: perhaps the largest internet chemistry directory
• Sheffield Chemputer: interactive chemistry calculators on the WWW