NO. 081Post-Transition

Tl

Thallium

Thallium is a soft, malleable post-Transition known for its extreme toxicity. It was historically used in rodenticides and electronics, but its applications are now tightly controlled due to severe health risks.

Crystal Structure

Hexagonal close-packed (hcp)

Technical Specifications

Atomic Mass204.38 u

Density11.85 g/cm³

Melting Point577 K

Boiling Point1746 K

Atomic Radius156 pm

Electronegativity1.62

Ionization Energy589 kJ/mol

Electron Affinity19 kJ/mol

Bonding TypeMetallic

Oxidation States1, 3

Acid/BaseBasic

ReactivityMedium

Electron Configuration

[Xe] 4f14 5d10 6s2 6p1

Discovered ByWilliam Crookes

Year1861

Known Isotopes

Tl-203Tl-205