| Selenium | |
| Electrons per shell | 2,8,18,6 |
| Electron Configuration | [Ar] 3d10 4s2 4p4 ![]() |
| Ground state | 3P2 |
| Atomic Volume | 16.45 cm3 mol-1 |
| Electronegativity | 2.55 |
| Magnetic ordering | No data |
| Mass magnetic susceptibility | -4 x 10-9 |
| Molar magnetic susceptibility | -3.16 x 10-10 |
| Speed of sound | 3350 m s-1 |
Thermal Properties |
|
| Enthalpy of Atomization | 205.9 kJ mol-1 @25°C |
| Enthalpy of Fusion | 5.1 kJ mol-1 |
| Enthalpy of Vaporisation | 90 kJ mol-1 |
| Heat Capacity | 25.363 J mol-1 K-1 |
| Thermal Conductivity | 0.519 W m-1 K-1 |
| Thermal Expansion | 37 μm m-1 K-1 |
| Critcal Temperature | 1766 K (1493°C) |
| Critcal Pressure | No data. |
| Adiabatic index | No data. |
Hardness |
|
| Brinell hardness | 736 MPa |
| Mohs hardness | 2.0 |
Elastic Properties |
|
| Bulk modulus | 8.3 GPa |
| Poisson ratio | 0.33 |
| Shear modulus | 3.7 GPa |
| Young's modulus | 10 GPa |
Electrical Properties |
|
| Electrical resistivity | No data. |
| Electrical conductivity | 1 x 10-12 106/cm Ω |
Chemical Properties |
|
| Electrochemical Equivalent | 0.7365 g Ah-1 |
| Electron Work Function | 5.9 eV |
| Valence Electron Potential (-eV) | 120 |
| Ionization Potential | |
| 9.752 | |
| 21.19 | |
| 30.82 | |
| Incompatibilities | Acids, strong oxidizers, chromium trioxide (CrO3), potassium bromate (BrKO3), cadmium. |
Flammability |
|
Optical Properties |
|
| Refractive Index (gas) | 1.000895 |
Energy Levels |
|
| 11.2224 KeV | |
| 11.1814 KeV | |
| 12.4959 KeV | |
| 12.6504 KeV | |
| 12.4869 KeV | |
| 1.3791 KeV | |
| 1.3791 KeV | |
| 1.41923 KeV | |
| 1.489 KeV | |
| 1.49 KeV | |
| 1.244 KeV | |
| 1.2061 KeV | |
Atomic Radii |
|
| 115 pm | |
| 103 pm | |
| 116 pm | |
| 190 pm | |
| 107 pm | |
| No data. | |
Ionic Radii (Å) |
||||
| Charge | Coordination | Crystal | Ionic | Key |
| -2 | VI | 1.84 | 1.98 | P |
| 4 | VI | 0.64 | 0.5 | A |
| 6 | IV | 0.42 | 0.28 | * |
| VI | 0.56 | 0.42 | C | |
| R, From r3 vs V plots. |
| C, Calculated from bond length - bond strength equations. |
| E, Estimated. |
| *, Most Reliable. |
| M, From Metallic Oxides. |
| A, Ahrens (1952) Ionic radius. |
| P, Pauling's (1960) Crystal Radius. |
Oxidation States |
|
| Se+4, Se+6 | |
| Se-2, Se+1, Se+2 | |
Ionisation Energies (kJ mol-1) ![]() |
|
| 940.9 | |
| 2044 | |
| 2974 | |
| 4144 | |
| 6590 | |
| 7883 | |
| 14990 | |
| 19500 | |
| 23300 | |
| 27200 | |
Covalent Bonds (kJ mol-1) |
|
| 305 | |
| 245 | |
| 343 | |
| 285 | |
| 245 | |
| 330 | |
Vapour Pressure |
||||||
| P (Pa) | 1 | 10 | 100 | 1K | 10K | 100K |
| T (K) | 500 | 552 | 617 | 704 | 813 | 958 |
Crystal Structure |
|
| Monoclinic | |
![]() |
a = 905.4 pm |
| b = 908.3 pm | |
| c = 1160.1 pm | |
| α = 90° | |
| β = 90.810° | |
| γ = 90° | |