Thallium (Tl)
Thallium is the chemical element with atomic number 81 and symbol Tl. It is a post-transition metal in period 6, group 13, with a standard atomic weight of 204.38 u.
Key facts
- Z
- 81
- Atomic weight
- 204.38 u
- Category
- post-transition metal
- State at 298 K
- Solid
- Occurrence
- primordial
- Discovered
- 1861
- CAS
- 7440-28-0
Measured properties
| Property | Value | Source |
|---|---|---|
| Electronegativity | 1.62 | National Center for Biotechnology Information (NIH) |
| Melting point | 577 K | National Center for Biotechnology Information (NIH) |
| Boiling point | 1,746 K | National Center for Biotechnology Information (NIH) |
| Density stp | 11.8 g/cm³ | National Center for Biotechnology Information (NIH) |
| Atomic radius empirical | 196 pm | National Center for Biotechnology Information (NIH) |
| Ionization energy 1st | 589.3 kJ/mol | National Center for Biotechnology Information (NIH) |
| Electron affinity | 19.3 kJ/mol | National Center for Biotechnology Information (NIH) |
Electron configuration
- Noble gas notation
- [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹
- Full notation
- 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p¹
- Electrons per shell
- 2, 8, 18, 32, 18, 3