Selenium

Selenium (Se)

Metalloid element, belongs to group 16 of the periodic table. Multiple allotropic forms exist. Chemically resembles sulphur. Discovered in 1817 by Jons J. Berzelius.
Atomic Number34
Atomic Weight78.971
Mass Number80
Group16
Period4
Blockp
Protons34 p+
Neutrons46 n0
Electrons34 e-
Selen 1.jpg Animated Bohr Model Enhanced Bohr Model Bohr Model Orbital Diagram

Properties

Atomic Radius
115 pm
Atomic Volume
Covalent Radius
115.99999999999999 pm
Metallic Radius
117 pm
Ionic Radius
198 pm
Crystal Radius
184 pm
Van der Waals radius
190 pm
Density
4.809 g/cm³
Boiling Point
958.1 K
Melting Point
490 K
Electrons per shell2, 8, 18, 6
Electronegativity
2.55
Electrophilicity
2.240849270962 eV/particle
Proton Affinity
Electron Affinity
2.02067 eV/particle
Ionization Potential
9.752392 eV/particle
Heat of Vaporization
59.7 kJ/mol
Heat of Fusion
5.23 kJ/mol
Heat of Formation
227.2 kJ/mol
Molar Heat Capacity
25.363 J/(mol K)
Specific Heat Capacity
0.321 J/(g⋅K)
Thermal Conductivity
0.52 W/(m K)
Gas Basicity
Dipole Polarizability
28.9 a₀
C6 Dispersion Coefficient
210 a₀
Oxidation States-2, 2, 4, 6
Color
Gray
Crystal StructureSimple Monoclinic (HEX)
Lattice Constant
4.36 Å
Bulk Modulus
Electrical Resistivity
Electron Configuration[Ar] 3d10 4s2 4p4
Magnetic Ordering
Magnetic Susceptibility
PhaseSolid
Poisson Ratio
Shear Modulus
Young's Modulus
Allotropes
Alternate Names
Adiabatic Index
Appearance
Electric Conductivity
Critical Pressure
Critical Temperature
Curie Point
Electrical
Hardness
Magnetic Susceptibility
Magnetic
Neel Point
Neutron Cross Section
Neutron Mass Absorption
Gas Phase
Quantum Numbers
Refractive Index
Space Group
Speed of Sound
Superconducting Point
Thermal Expansion
Valence Electrons
Classification
CategoryOther nonmetals, Nonmetals
CAS GroupVIB
IUPAC GroupVIA
Glawe Number95
Mendeleev Number101
Pettifor Number93
Geochemical Classsemi-volatile
Goldschmidt Classchalcophile
Radioactivity
RadioactiveNo
Decay Mode
Half-Life
Lifetime
Abundance
Abundance in Earth's crust
0.05 mg/kg
Abundance in Oceans
0.0002 mg/L
Abundance in Human Body
Abundance in Meteor
Abundance in Sun
Abundance in Universe3×10-6%

Isotopes of Selenium

Stable Isotopes
74Se 76Se 77Se 78Se 80Se 82Se
Unstable Isotopes
65Se 66Se 67Se 68Se 69Se 70Se 71Se 72Se 73Se 75Se 79Se 81Se 83Se 84Se 85Se 86Se 87Se 88Se 89Se 90Se 91Se 92Se 93Se 94Se

History

Selenium was first observed in about the year 1300 by the alchemist Arnold of Villanova. Selenium was discovered in 1817 by Jöns Jacob Berzelius and Johan Gottlieb Gahn who noted the similarity of the new element to the previously-known tellurium. In 1873, Willoughby Smith found that the electrical resistance of grey selenium was dependent on the ambient light. From the Greek word Selene, moon

DiscoverersJöns Berzelius
Discovery LocationSweden
Discovery Year1818
Name OriginGreek: selênê (moon).
Many of selenium's compounds, such as selenates and selenites, are highly toxic
Selenium deficiency in animals can lead to slow growth

Uses

Selenium is used in the glass industry to decolorize glass and to make red-colored glasses and enamels. It is used as a catalyst in many chemical reactions. It is also used as a photographic toner, and as an additive to stainless steel. Selenium sulfide is used in anti-dandruff shampoos. Light causes it to conduct electricity more easily. It is used in photoelectric cells, TV cameras, xerography machines and as a semiconductor in solar batteries and rectifiers. Also colors glass red.

Sources

Obtained from lead, copper and nickel refining. Conducts electricity when struck by light.