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 of Se (Selenium) Enhanced Bohr Model of Se (Selenium) Bohr Model: Se (Selenium) Orbital Diagram of Se (Selenium)

Properties

Atomic Radius
115 pm
Molar Volume
Covalent Radius
116 pm
Metallic Radius
117 pm
Ionic Radius
198 pm
Crystal Radius
184 pm
Van der Waals Radius
190 pm
Density
4.809 g/cm³
Energy
Proton Affinity
Electron Affinity
2.02067 eV/particle
Ionization Energy
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
Electrons
Electron Shells2, 8, 18, 6
Valence Electrons6
Electron Configuration[Ar] 3d10 4s2 4p4
Oxidation States-2, -1, 0, 1, 2, 3, 4, 5, 6
Electronegativity
2.55
Electrophilicity
2.2408492709619536 eV/particle
Phases
PhaseSolid
Gas Phase
Boiling Point
958.15 K
Melting Point
453.15 K
Critical Pressure
Critical Temperature
1,766.15 K
Triple Point
Visual
Color
Gray
Appearanceblack, red, and gray (not pictured) allotropes
Refractive Index
1.000895
Thermodynamic Properties
Thermal Conductivity
0.52 W/(m K)
Thermal Expansion
Molar Heat Capacity
25.363 J/(mol K)
Specific Heat Capacity
0.321 J/(g⋅K)
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
Type
Electrical Conductivity
Electrical Resistivity
Superconducting Point
Magnetism
Typediamagnetic
Magnetic Susceptibility (Mass)
-0.000000004 m³/Kg
Magnetic Susceptibility (Molar)
-0.000000000316 m³/mol
Magnetic Susceptibility (Volume)
-0.0000193
Magnetic Ordering
Curie Point
Neel Point
Structure
Crystal StructureSimple Monoclinic (HEX)
Lattice Constant
4.36 Å
Lattice Anglesπ/2, 1.58493, π/2
Mechanical Properties
Hardness
2 MPa
Bulk Modulus
8.3 GPa
Shear Modulus
3.7 GPa
Young Modulus
10 GPa
Poisson Ratio
0.33
Speed of Sound
3,350 m/s
Classification
CategoryOther nonmetals, Nonmetals
CAS GroupVIB
IUPAC GroupVIA
Glawe Number95
Mendeleev Number101
Pettifor Number93
Geochemical Classsemi-volatile
Goldschmidt Classchalcophile
Other
Gas Basicity
Dipole Polarizability
28.9 ± 1 a₀
C6 Dispersion Coefficient
210 a₀
AllotropesAmorphous Red Selenium, Amorphous Black Selenium, Monoclinic Selenium, Hexagonal Selenium
Neutron Cross Section
11.7
Neutron Mass Absorption
0.0056
Quantum Numbers3P2
Space Group14 (P121/c1)

Isotopes of Selenium

Stable Isotopes6
Unstable Isotopes27
Radioactive Isotopes28

63Se

AbundanceRadioactive ☢️
Relative Atomic Mass
62.981911 ± 0.000537 Da
Mass Number63
G-Factor
Half Life
13.2 ± 3.9 ms
Spin3/2
Quadrupole Moment
Discovery Year2016
Parity-

63Se Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)89%
2p (2-proton emission)0.5%

64Se

AbundanceRadioactive ☢️
Relative Atomic Mass
63.971165 ± 0.000537 Da
Mass Number64
G-Factor
0
Half Life
22.6 ± 0.2 ms
Spin0
Quadrupole Moment
0
Discovery Year2005
Parity+

64Se Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)%
β+ p (β+-delayed proton emission)%

65Se

AbundanceRadioactive ☢️
Relative Atomic Mass
64.964552 ± 0.000322 Da
Mass Number65
G-Factor
Half Life
34.2 ± 0.7 ms
Spin3/2
Quadrupole Moment
Discovery Year1993
Parity-

65Se Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)87%

66Se

AbundanceRadioactive ☢️
Relative Atomic Mass
65.955276 ± 0.000215 Da
Mass Number66
G-Factor
0
Half Life
54 ± 4 ms
Spin0
Quadrupole Moment
0
Discovery Year1993
Parity+

66Se Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)%

67Se

AbundanceRadioactive ☢️
Relative Atomic Mass
66.949994 ± 0.000072 Da
Mass Number67
G-Factor
Half Life
133 ± 4 ms
Spin5/2
Quadrupole Moment
Discovery Year1991
Parity-

67Se Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)0.5%

68Se

AbundanceRadioactive ☢️
Relative Atomic Mass
67.941825236 ± 0.000000532 Da
Mass Number68
G-Factor
0
Half Life
35.5 ± 0.7 s
Spin0
Quadrupole Moment
0
Discovery Year1990
Parity+

68Se Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

69Se

AbundanceRadioactive ☢️
Relative Atomic Mass
68.939414845 ± 0.000001599 Da
Mass Number69
G-Factor
Half Life
27.4 ± 0.2 s
Spin1/2
Quadrupole Moment
0
Discovery Year1974
Parity-

69Se Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)0.052%

70Se

AbundanceRadioactive ☢️
Relative Atomic Mass
69.933515521 ± 0.0000017 Da
Mass Number70
G-Factor
0
Half Life
41.1 ± 0.3 m
Spin0
Quadrupole Moment
0
Discovery Year1950
Parity+

70Se Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

71Se

AbundanceRadioactive ☢️
Relative Atomic Mass
70.932209431 ± 0.000003 Da
Mass Number71
G-Factor
Half Life
4.74 ± 0.05 m
Spin5/2
Quadrupole Moment
Discovery Year1957
Parity-

71Se Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

72Se

AbundanceRadioactive ☢️
Relative Atomic Mass
71.927140506 ± 0.0000021 Da
Mass Number72
G-Factor
0
Half Life
8.4 ± 0.08 d
Spin0
Quadrupole Moment
0
Discovery Year1948
Parity+

72Se Decay Modes
Decay ModeIntensity
ϵ (electron capture)100%

73Se

AbundanceRadioactive ☢️
Relative Atomic Mass
72.926754881 ± 0.000007969 Da
Mass Number73
G-Factor
0.19822222222222 ± 0.0028888888888889
Half Life
7.15 ± 0.09 h
Spin9/2
Quadrupole Moment
Discovery Year1948
Parity+

73Se Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

74Se

Abundance
0.86 ± 0.03
Relative Atomic Mass
73.922475933 ± 0.000000015 Da
Mass Number74
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year1922
Parity+

74Se Decay Modes
Decay ModeIntensity
+ (double β+ decay)%

75Se

AbundanceRadioactive ☢️
Relative Atomic Mass
74.92252287 ± 0.000000078 Da
Mass Number75
G-Factor
0.2732 ± 0.004
Half Life
119.78 ± 0.03 d
Spin5/2
Quadrupole Moment
1.1 ± 0.2
Discovery Year1947
Parity+

75Se Decay Modes
Decay ModeIntensity
ϵ (electron capture)100%

76Se

Abundance
9.23 ± 0.07
Relative Atomic Mass
75.919213702 ± 0.000000017 Da
Mass Number76
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year1922
Parity+

77Se

Abundance
7.6 ± 0.07
Relative Atomic Mass
76.91991415 ± 0.000000067 Da
Mass Number77
G-Factor
1.06712 ± 0.0001
Half Life
Spin1/2
Quadrupole Moment
0
Discovery Year1922
Parity-

78Se

Abundance
23.69 ± 0.22
Relative Atomic Mass
77.917309244 ± 0.000000191 Da
Mass Number78
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year1922
Parity+

79Se

AbundanceRadioactive ☢️
Relative Atomic Mass
78.918499252 ± 0.000000238 Da
Mass Number79
G-Factor
-0.29085714285714 ± 0.0042857142857143
Half Life
327 ± 28 ky
Spin7/2
Quadrupole Moment
0.8 ± 0.2
Discovery Year1950
Parity+

79Se Decay Modes
Decay ModeIntensity
β (β decay)100%

80Se

Abundance
49.8 ± 0.36
Relative Atomic Mass
79.916521761 ± 0.000001016 Da
Mass Number80
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year1922
Parity+

80Se Decay Modes
Decay ModeIntensity
(double β decay)%

81Se

AbundanceRadioactive ☢️
Relative Atomic Mass
80.917993019 ± 0.000001049 Da
Mass Number81
G-Factor
Half Life
18.45 ± 0.12 m
Spin1/2
Quadrupole Moment
0
Discovery Year1948
Parity-

81Se Decay Modes
Decay ModeIntensity
β (β decay)100%

82Se

AbundanceRadioactive ☢️
8.82 ± 0.15
Relative Atomic Mass
81.916699531 ± 0.0000005 Da
Mass Number82
G-Factor
0
Half Life
87.6 ± 1.5 Ey
Spin0
Quadrupole Moment
0
Discovery Year1922
Parity+

82Se Decay Modes
Decay ModeIntensity
(double β decay)100%

83Se

AbundanceRadioactive ☢️
Relative Atomic Mass
82.919118604 ± 0.000003259 Da
Mass Number83
G-Factor
Half Life
22.25 ± 0.04 m
Spin9/2
Quadrupole Moment
Discovery Year1937
Parity+

83Se Decay Modes
Decay ModeIntensity
β (β decay)100%

84Se

AbundanceRadioactive ☢️
Relative Atomic Mass
83.918466761 ± 0.000002105 Da
Mass Number84
G-Factor
0
Half Life
3.26 ± 0.1 m
Spin0
Quadrupole Moment
0
Discovery Year1960
Parity+

84Se Decay Modes
Decay ModeIntensity
β (β decay)100%

85Se

AbundanceRadioactive ☢️
Relative Atomic Mass
84.922260758 ± 0.000002804 Da
Mass Number85
G-Factor
Half Life
32.9 ± 0.3 s
Spin5/2
Quadrupole Moment
Discovery Year1960
Parity

85Se Decay Modes
Decay ModeIntensity
β (β decay)100%

86Se

AbundanceRadioactive ☢️
Relative Atomic Mass
85.924311732 ± 0.000002705 Da
Mass Number86
G-Factor
0
Half Life
14.3 ± 0.3 s
Spin0
Quadrupole Moment
0
Discovery Year1973
Parity+

86Se Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%

87Se

AbundanceRadioactive ☢️
Relative Atomic Mass
86.928688616 ± 0.000002405 Da
Mass Number87
G-Factor
Half Life
5.5 ± 0.06 s
Spin3/2
Quadrupole Moment
Discovery Year1968
Parity+

87Se Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)0.6%

88Se

AbundanceRadioactive ☢️
Relative Atomic Mass
87.93141749 ± 0.000003604 Da
Mass Number88
G-Factor
0
Half Life
1.53 ± 0.06 s
Spin0
Quadrupole Moment
0
Discovery Year1970
Parity+

88Se Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)0.99%

89Se

AbundanceRadioactive ☢️
Relative Atomic Mass
88.936669058 ± 0.000004003 Da
Mass Number89
G-Factor
Half Life
430 ± 50 ms
Spin5/2
Quadrupole Moment
Discovery Year1971
Parity+

89Se Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)7.8%

90Se

AbundanceRadioactive ☢️
Relative Atomic Mass
89.940096 ± 0.000354 Da
Mass Number90
G-Factor
0
Half Life
210 ± 80 ms
Spin0
Quadrupole Moment
0
Discovery Year1994
Parity+

90Se Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%

91Se

AbundanceRadioactive ☢️
Relative Atomic Mass
90.9457 ± 0.000465 Da
Mass Number91
G-Factor
Half Life
270 ± 50 ms
Spin1/2
Quadrupole Moment
0
Discovery Year1975
Parity+

91Se Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)21%
2n (2-neutron emission)%

92Se

AbundanceRadioactive ☢️
Relative Atomic Mass
91.94984 ± 0.000429 Da
Mass Number92
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year1997
Parity+

92Se Decay Modes
Decay ModeIntensity
β (β decay)%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

93Se

AbundanceRadioactive ☢️
Relative Atomic Mass
92.956135 ± 0.000429 Da
Mass Number93
G-Factor
Half Life
Spin1/2
Quadrupole Moment
0
Discovery Year1997
Parity+

93Se Decay Modes
Decay ModeIntensity
β (β decay)%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

94Se

AbundanceRadioactive ☢️
Relative Atomic Mass
93.96049 ± 0.000537 Da
Mass Number94
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year1997
Parity+

94Se Decay Modes
Decay ModeIntensity
β (β decay)%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

95Se

AbundanceRadioactive ☢️
Relative Atomic Mass
94.9673 ± 0.000537 Da
Mass Number95
G-Factor
Half Life
Spin3/2
Quadrupole Moment
Discovery Year2010
Parity+

95Se Decay Modes
Decay ModeIntensity
β (β decay)%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

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
Etymology (Name Origin)Greek: selênê (moon).
Pronunciationsi-LEE-ni-em (English)
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.

Abundance
Abundance in Earth's crust
0.05 mg/kg
Abundance in Oceans
0.0002 mg/L
Abundance in Human Body
0.000005 %
Abundance in Meteor
0.0013 %
Abundance in Sun
Abundance in Universe
0.000003 %

Nuclear Screening Constants

1s0.7378
2p3.9348
2s9.1116
3d15.523
3p15.295
3s14.5966
4p25.7128
4s24.2424