81 - Thallium post-transition metal
Discovered by William Crookes in 1861
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.
Periodic table
| Shell | Electrons | Orbitals |
|---|---|---|
| 1 | 2 | 2 in 1s |
| 2 | 8 | 2 in 2s + 6 in 2p |
| 3 | 18 | 2 in 3s + 6 in 3p + 10 in 3d |
| 4 | 32 | 2 in 4s + 6 in 4p + 10 in 4d + 14 in 4f |
| 5 | 18 | 2 in 5s + 6 in 5p + 10 in 5d |
| 6 | 3 | 2 in 6s + 1 in 6p |
Electron shells
silvery white Appearance
204 u Atomic Mass
1.9 Å Atomic Radius
1.75k K Boiling Point
13 Group
1, 3 Common Oxidation States
1.45 Å Covalent Radius
11.8 g/cm³ Density
36.4 kJ/mol Electron Affinity
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p1 Electron Configuration
[Xe] 4f14 5d10 6s2 6p1 Electron Configuration (semantic)
2.04 Electronegativity
81 Electrons
6.11 eV First Ionization Energy
1, 3 ICSD Oxidation States
589.4, 1971, 2878 kJ/mol Ionization Energies
577 K Melting Point
78 Mendeleev Number
26.3 J/(mol·K) Molar Heat
6 Number of Shells
3 Electron Valency
123 Neutrons
81 Atomic Number
28 Number of Isotopes
1, 3 Oxidation States
6 Period
Solid Phase
81 Protons
2, 8, 18, 32, 18, 3 Electron Shell Occupations
0.129 J/(g K) Specific Heat