81 Tl 204.38
Thallium
Post-Transition Metal
Thallium (Tl) is a chemical element with atomic number 81, classified as a post-transition metal. At room temperature it is a solid. It was discovered in 1861 by William Crookes.
Properties
- Atomic number
- 81
- Atomic mass
- 204.38 u
- Category
- Post-Transition Metal
- Group
- 13
- Period
- 6
- Block
- p-block
- Electron configuration
- [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹
- Phase at STP
- Solid
- Density
- 11.85 g/cm³
- Melting point
- 577 K (303.9 °C)
- Boiling point
- 1746 K (1472.8 °C)
- Electronegativity
- 1.62
- Atomic radius
- 156 pm
- Ionization energy
- 6.108 eV
- Discovery
- 1861 · William Crookes
Common uses
Electronics, glass, semiconductors, medical imaging
Did you know?
Extremely toxic and once used as rat poison and insecticide.