81Tl204.383
Thallium
Post-Transition Metal
Solid at STP
Period 6Group 13Block PDiscovered 1861
[Xe]6s2 4f14 5d10 6p1
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.
📖 Read more on Wikipedia →Atomic Properties
| Atomic Number | 81 |
| Atomic Mass | 204.383 u |
| Electron Configuration | [Xe]6s2 4f14 5d10 6p1 |
| Oxidation States | +3, +1 |
| Electronegativity | 1.62 (Pauling) |
| Atomic Radius | 196 pm |
| Ionization Energy | 6.108 eV |
| Electron Affinity | 0.2 eV |
| Block | P |
Physical Properties
| Appearance | silvery white |
| Standard State | Solid |
| Melting Point | 577 K (303.9 °C) |
| Boiling Point | 1746 K (1472.8 °C) |
| Density | 11.8 g/cm³ |
| Molar Heat | 26.32 J/(mol·K) |
| CPK Color | #A6544D |
Classification
| Category | Post-Transition Metal |
| Group Block | Post-transition metal |
| Period | 6 |
| Group | 13 |
| Block | P |
Discovery
| Year Discovered | 1861 |
| Discovered By | William Crookes |
| Electron Shells | 2, 8, 18, 32, 18, 3 |