#34
Selenium
polyatomic nonmetal· Solid·78.9718 u
Selenium is a chemical element with symbol Se and atomic number 34. It is a nonmetal with properties that are intermediate between those of its periodic table column-adjacent chalcogen elements sulfur and tellurium. It rarely occurs in its elemental state in nature, or as pure ore compounds.
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Identity
- Symbol
- Se
- Atomic Number
- 34
- Atomic Mass
- 78.9718 u
- Category
- polyatomic nonmetal
- Block
- p-block
- Period
- 4
- Group
- 16
- Appearance
- black, red, and gray (not pictured) allotropes
- Year Discovered
- 1817 CE
- Discovered By
- Jöns Jakob Berzelius
- Named By
- Moon
Electrons
- Configuration
- [Ar] 3d10 4s2 4p4
- Full Configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4
- Shells
- 2, 8, 18, 6
- Electronegativity
- 2.55
- Electron Affinity
- 194.9587
- Oxidation States
- +6, +4, -2
- Ionization Energies
- 941, 2045, 2973.7, 4144, 6590 … +2 more
Physical Properties
- State at
- Solid
- Melting Point
- 494
- Boiling Point
- 958
- Density
- 4.81
- Molar Heat
- 25.363 J/(mol·K)
- Crystal Structure
- HEX
- Magnetic Ordering
- Diamagnetic
Mechanical
- Atomic Radius
- 103 pm
- Covalent Radius
- 120 pm
- Van der Waals
- 190 pm
- Mohs Hardness
- 2
- Bulk Modulus
- 8.3 GPa GPa
Thermal & Electrical
- Thermal Conductivity
- 0.52 W/(m K) W/(m·K)
- Specific Heat
- 321 J/(kg K) J/(g·K)
- Heat of Vaporization
- 95.5 kJ/mol kJ/mol
- Heat of Fusion
- 6.69 kJ/mol kJ/mol
Abundance
- Universe
- 90.0 ppb
- Sun
- 0
- Meteorite
- 13 ppm
- Earth's Crust
- 4.28 ppm
- Ocean
- 90.0 ppt
- Human Body
- 50.0 ppb