Colourless, tasteless and lethal — thallium was the poisoner's element until detection caught up.
- Atomic number
- 81
- Atomic mass
- 204.38 u
- Phase
- Solid
- Electron configuration
- [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹
- Melting point
- 577 K · 303.9 °C
- Boiling point
- 1,746 K · 1,472.9 °C
- Density
- 11.85 g/cm³
- Electronegativity
- 1.62
- Period / Group
- 6 / 13
- Discovery year
- 1861