Element Thallium

Thallium ElementIt is a chemical element with the symbol Tl and atomic number 81.
It is a gray post-transition metal that is not found free in nature.
When isolated, thallium resembles tin, but discolors when exposed to air.
Chemists William Crookes and Claude-Auguste Lamy discovered Element Thallium independently in 1861, in residues of sulfuric acid production.

Names and Identifiers

Chemical Formula:TI
CAS:7440-28-0
Molecular Weight:204.38300 g/mol
EC Number :231-138-1
MDL Number:MFCD00134063
Color:silvery-gray
Other Names:n/a
PubChem CID:5359464
IUPAC Name:Thallium
Inchl:InChI=1S/TI
InChI Key:BKVIYDNLLOSFOA-UHFFFAOYSA-N
Canonical SMILES:[TI]
ICSC Number:0077

Physical & Chemical Properties

Phase:Solid
Density:11.85 g/cm3
Boiling Point:1746 K ​(1473 °C, ​2683 °F)
Melting Point:577 K ​(304 °C, ​579 °F)
Molecular Formula:TI
Flash Point:n/a
Exact Mass:204.97400
Symbol:Globally Harmonized System of ClassificationGlobally Harmonized System of Classification
Signal Word:Danger
Hazard Statements:H300 + H330-H373-H413
Precautionary Statements:P260-P264-P284-P301 + P310-P310
Hazard Codes:Xn,T+
Risk Phrases:26/28-33-53-36/37/38-20/22-36/38
Safety Phrases:S13-S28-S45-S61-S36/37/39-S36/37-S26
RIDADR:UN 3288 6.1/PG 2
WGK Germany:3
RTECS:XG3425000
Packaging Group:II
Hazard Class:6.1

Thallium has 25 isotopes which have atomic masses that range from 184 to 210.

Naturally occurring isotopes

IsotopeMass/DaNatural abundance (atom %)Nuclear spin (I)Magnetic moment (μ/μN)
203Tl202.972320 (5)29.524 (14)1/21.622257
205Tl204.974401 (5)70.476 (14)1/21.6382135

Radiosotope data

IsotopeMass/DaHalf-lifeMode of decayNuclear spinNuclear magnetic moment
200Tl199.970951.087 dEC to 200Hg20.04
201Tl200.970783.040 dEC to 201Hg1/21.605
202Tl201.9720912.23 dEC to 202Hg20.06
204Tl203.973853.78 yEC to 204Hg; β to 204Pb20.09

We’re ready to partner with you.