81Solid
Tl 204.383 Atomic mass · uPost-transition metals
Thallium
Thallium is a chemical element with symbol Tl and atomic number 81. This soft gray post-transition metal is not found free in nature. When isolated, it resembles tin, but discolors when exposed to air.
Discovery 1861 (William Crookes)
K2L8M18N32O18P3
Physical properties
Values for the element in its standard state.
- Density
- 11.85g/cm³
- Melting point
- 577K
- Boiling point
- 1,746K
- Atomic radius
- 148pm
- Bonding type
- Metallic
- Molar heat
- 26.32J/(mol·K)
Inside the atom
Electron arrangement and the energy behind its behavior.
Full electron configuration
1s, 2 electrons; 2s, 2 electrons; 2p, 6 electrons; 3s, 2 electrons; 3p, 6 electrons; 3d, 10 electrons; 4s, 2 electrons; 4p, 6 electrons; 4d, 10 electrons; 5s, 2 electrons; 5p, 6 electrons; 4f, 14 electrons; 5d, 10 electrons; 6s, 2 electrons; 6p, 1 electrons;
[Xe] represents 54 core electrons. The full view shows them explicitly.
81 electrons Orbital order preserved from source
- Electronegativity
- 2.04Pauling scale
- First ionization energy
- 589kJ/mol
- Electron affinity
- 19kJ/mol
- Van der Waals radius
- 196pm
Tl ThalliumAtomic number 81
589kJ/mol
Atomic numberGaps indicate unavailable data
About thallium
- Appearance
- Silvery white
- Discovery
- 1861 (William Crookes)
- Data source
- Read the reference
A missing value means it is unavailable in this reference dataset. Values can vary with measurement method and conditions.