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Technical data for Selenium

Click any property name to see plots of that property for all the elements.

Overview
NameSelenium
SymbolSe
Atomic Number34
Atomic Weight78.96
Density4.819 g/cm3
Melting Point221 °C[note]
Boiling Point685 °C

Thermal properties
PhaseSolid
Melting Point221 °C[note]
Boiling Point685 °C
Absolute Melting Point494 K[note]
Absolute Boiling Point958 K
Critical Pressure27.2 MPa (268.4 Atm)
Critical Temperature1766 K
Heat of Fusion5.4 kJ/mol
Heat of Vaporization26 kJ/mol
Heat of Combustion{"N/A", "N/A", "N/A"} J/(kg K)
Specific Heat321.2 J/(kg K)[note]
Adiabatic IndexN/A
Neel PointN/A
Thermal Conductivity0.52 W/(m K)
Thermal ExpansionN/A

Bulk physical properties
Density4.819 g/cm3
Density (Liquid)3.99 g/cm3
Molar Volume0.000016385
Brinell Hardness736 MPa
Mohs Hardness2 MPa
Vickers HardnessN/A
Bulk Modulus8.3 GPa
Shear Modulus3.7 GPa
Young Modulus10 GPa
Poisson Ratio0.33
Refractive Index1.000895
Speed of Sound3350 m/s
Thermal Conductivity0.52 W/(m K)
Thermal ExpansionN/A

Reactivity
Valence6
Electronegativity2.55
ElectronAffinity195 kJ/mol
Ionization Energies
941, 2045, 2973.7, 4144, 6590, 7880, 14990 kJ/mol

Health and Safety
Autoignition PointN/A
FlashpointN/A[note]
Heat of Combustion{"N/A", "N/A", "N/A"} J/(kg K)
DOT Hazard Class{N/A, 6.1, N/A}
DOT Numbers"N/A", {2658}, "N/A"
EU Number{N/A, N/A, N/A}
NFPA Fire Rating{N/A, 0, N/A}
NFPA Hazards
N/ A, N/ A, N/ A
NFPA Health Rating{N/A, 2, N/A}
NFPA Reactivity Rating{N/A, 0, N/A}
RTECS Number{N/A, RTECSVS7700000, N/A}
NFPA LabelNFPA Label[note]

Classifications
Alternate NamesNone
Names of Allotropes
AmorphousRedSelenium, AmorphousBlackSelenium, MonoclinicSelenium, HexagonalSelenium
Blockp
Group16
Period4
Electron Configuration[Ar]3d104s24p4
ColorGray
Discovery
1817 in Sweden
Gas phaseN/A
CAS NumberCAS7782-49-2
CID Number{CID6326970, CID6326970, CID139346}
Gmelin Number{N/A, N/A, N/A}
NSC Number{N/A, N/A, N/A}
RTECS Number{N/A, RTECSVS7700000, N/A}

Electrical properties
Electrical TypeN/A
Electrical ConductivityN/A
ResistivityN/A
Superconducting PointN/A

Magnetic properties
Magnetic TypeDiamagnetic
Curie PointN/A
Mass Magnetic Susceptibility-4×10-9
Molar Magnetic Susceptibility-3.16×10-10
Volume Magnetic Susceptibility-0.0000193

Abundances
% in Universe3×10-6%
% in SunN/A
% in Meteorites0.0013%
% in Earth's Crust5×10-6%
% in Oceans4.5×10-8%
% in Humans5×10-6%

Atomic dimensions and structure
Atomic Radius103 pm
Covalent Radius116 pm
Van der Waals Radius190 pm
Crystal StructureSimple Monoclinic
Lattice Angles
π/2, 1.58493, π/2
Lattice Constants
905.4, 908.3, 1160.1 pm
Space Group NameP121/c1
Space Group Number14

Nuclear Properties
Half-LifeStable
LifetimeStable
Decay ModeN/A
Quantum Numbers3P2
Neutron Cross Section11.7
Neutron Mass Absorption0.0056
Known Isotopes
65Se, 66Se, 67Se, 68Se, 69Se, 70Se, 71Se, 72Se, 73Se, 74Se, 75Se, 76Se, 77Se, 78Se, 79Se, 80Se, 81Se, 82Se, 83Se, 84Se, 85Se, 86Se, 87Se, 88Se, 89Se, 90Se, 91Se, 92Se, 93Se, 94Se
Stable Isotopes
74Se, 76Se, 77Se, 78Se, 80Se
Isotopic Abundances
74Se0.89%
76Se9.37%
77Se7.63%
78Se23.77%
80Se49.61%
82Se8.73%


Notes on the properties of Selenium:

Absolute Melting Point: Value given for hexagonal, gray form.

Melting Point: Value given for hexagonal, gray form.

Specific Heat: Value given for solid hexagonal form.

Flash Point: {Missing[NotAvailable], Missing[NotAvailable], Missing[NotAvailable]}

N FP ALabel: {Missing[NotAvailable], Missing[NotAvailable], Missing[NotAvailable]}

Up to date, curated data provided by
Mathematica's ElementData function from Wolfram Research, Inc.

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