Thallium · Tl Thallium
Used in certain optical and electronic materials; thallium and its compounds are highly toxic.
- atomic number / Atomic number
- 81
- atomic weight / Atomic mass
- 204.383 u
- Family/Group
- 13
- Period · Block / Period · Block
- 6 · p
- Category / Category
- post-transition metal · Post-transition metal
- State / State
- solid state
- Electron configuration
- [Xe]6s2 4f14 5d10 6p1
- Oxidation states / Oxidation states
- +3, +1
- Electronegativity / Electronegativity
- 1.62（Pauling）
- Density / Density
- 11.8 g/cm³
- Melting point / Melting point
- 577 K
- Boiling point / Boiling point
- 1746 K
- Atomic radius / Atomic radius
- 196 pm（van der Waals）
- First ionization energy
- 6.108 eV
- Discovery year / Discovery
- 1861
attribute description and data source
properties taken from PubChem periodic table snapshot (2026-10-04). Atomic weights may be reference values or representative isotope masses and cannot be considered exact constants for all samples; density, phase transition points, and phase states depend on temperature, pressure, and allotropes. The solidification of helium requires pressure. Some properties of radioactive and superheavy elements are predicted values, and missing items are marked as not included. Please check the original source and experimental conditions for precise calculations.