Selenium

Symbol | Se
Latin name | Selenium
Atomic number | 34
Period | 4
Element category | Nonmetals
Relative atomic mass | 78.96
Group | VI.A
Electronegativity | 2.4
Oxidation numbers | -2, 2, 4, 6
Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p4
Density [g/cm3] | 4.80
State | Solid
Melting point [°C] | 217
Boiling point [°C] | 685
Critical point [°C] | 1493
Critical pressure [MPa] | 27.2
Thermal conductivity [W m-1K-1] | 2.04
Heat capacity [J K-1g-1] | 0.32
Discovery | 1817
Hardness [Mohs scale] | 2.0
Brinell hardness [MPa] | 736
Young's modulus [GPa] | 10
Electrical conductivity [S m-1] | 8 · 106
Shear modulus [GPa] | 3.7
1.st ionization energy [eV] | 9.7524
2.nd ionization energy [eV] | 21.19
3.rd ionization energy [eV] | 30.82
Stable isotopes | 6
Unstable isotopes | 14