Selenium Element (Periodic Table)

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Selenium

Selenium (Se) is a chemical element of the periodic table, located in the group 16 and the period 4, and has the atomic number 34. It is a red powder or black reactive nonmetal, whose name comes from the Greek word “selene”, which means Moon. It is a member of the chalcogen group.

group
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
period
1
 1
H
 2
He
2
 3
Li
 4
Be
 5
B
 6
C
 7
N
 8
O
 9
F
 10
Ne
3
 11
Na
 12
Mg
 13
Al
 14
Si
 15
P
 16
S
 17
Cl
 18
Ar
4
 19
K
 20
Ca
 21
Sc
 22
Ti
 23
V
 24
Cr
 25
Mn
 26
Fe
 27
Co
 28
Ni
 29
Cu
 30
Zn
 31
Ga
 32
Ge
 33
As
 34
Se
 35
Br
 36
Kr
5
 37
Rb
 38
Sr
 39
Y
 40
Zr
 41
Nb
 42
Mo
 43
Tc
 44
Ru
 45
Rh
 46
Pd
 47
Ag
 48
Cd
 49
In
 50
Sn
 51
Sb
 52
Te
 53
I
 54
Xe
6
 55
Cs
 56
Ba
 72
Hf
 73
Ta
 74
W
 75
Re
 76
Os
 77
Ir
 78
Pt
 79
Au
 80
Hg
 81
Tl
 82
Pb
 83
Bi
 84
Po
 85
At
 86
Rn
7
 87
Fr
 88
Ra
 104
Rf
 105
Db
 106
Sg
 107
Bh
 108
Hs
 109
Mt
 110
Ds
 111
Rg
 112
Cn
 113
Nh
 114
Fl
 115
Mc
 116
Lv
 117
Ts
 118
Og
57
La
 58
Ce
 59
Pr
 60
Nd
 61
Pm
 62
Sm
 63
Eu
 64
Gd
 65
Tb
 66
Dy
 67
Ho
 68
Er
 69
Tm
 70
Yb
 71
Lu
89
Ac
 90
Th
 91
Pa
 92
U
 93
Np
 94
Pu
 95
Am
 96
Cm
 97
Bk
 98
Cf
 99
Es
 100
Fm
 101
Md
 102
No
 103
Lr
– p block

FAQs on Selenium Element

Selenium
‣ What does selenium look like?

Appearance: grey metallic-looking, red, and vitreous black (not pictured) allotropes
‣ Who discovered selenium? When was selenium discovered?

Discovery and first isolation: Jons Jakob Berzelius and Johann Gottlieb Gahn (1817)
‣ Where is selenium located on the periodic table?

Selenium Periodic Table

Location: Selenium is found in the fourth row of the periodic table below the sulfur element.
‣ What is selenium’s atomic number?

Atomic number (Z): 34
‣ What is the symbol for selenium?

Symbol: Se
‣ What is the atomic weight of selenium?

Standard atomic weight: 78.971
‣ What is the block of selenium?

Block: p-block
‣ What group is selenium in on the periodic table?

Group: 16 (chalcogens)
‣ Which period is selenium on the periodic table?

Period: 4
‣ What is the atomic radius of selenium (atomic number 34)?

Atomic radius: empirical: 120 pm
‣ Selenium covalent radius: 120±4 pm
‣ Selenium Van der Waals radius: 190 pm
‣ What is the melting point of selenium?

Melting point: 494 K (221 °C, 430 °F)
‣ What is the boiling point of selenium?

Boiling point: 958 K (685 °C, 1265 °F)
‣ Selenium critical point: 1766 K, 27.2 MPa
‣ How many electron shells does selenium have?

Electrons per shell: 2, 8, 18, 6
‣ What is the ground state electron configuration of selenium?

Electron configuration: [Ar] 3d10 4s2 4p4
‣ What is the ionization energy of selenium?

Ionization energies:
1st: 941.0 kJ/mol
2nd: 2045 kJ/mol
3rd: 2973.7 kJ/mol
‣ What is the phase of selenium at room temperature?

Phase (at r.t): solid
‣ What is the density of selenium?

Density (near r.t): gray: 4.81 g/cm3
alpha: 4.39 g/cm3
vitreous: 4.28 g/cm3

when liquid (at m.p): 3.99 g/cm3
‣ Selenium magnetic ordering: diamagnetic
‣ Selenium natural occurrence: primordial
‣ What is the oxidation state of selenium?

Oxidation state: 0, -2, +4, +6
‣ What’s the electronegativity of selenium?

Electronegativity: Pauling scale: 2.55
‣ Selenium poisson’s ratio: 0.33
‣ Selenium heat of fusion: gray: 6.69 kJ/mol
‣ Selenium heat of vaporization: 95.48 kJ/mol
‣ Selenium molar heat capacity: 25.363 J/(mol K)
‣ Selenium molar magnetic susceptibility: -25.0 × 10-6 cm3/mol (298 K)
‣ Speed of sound in selenium: 3350 m/s (at 20 °C)
‣ Selenium crystal structure: hexagonal
‣ Thermal expansion of selenium: amorphous: 37 µm/(m.K) (at 25 °C)
‣ Thermal conductivity of selenium: amorphous: 0.519 W/(m.K)
‣ What is the hardness of selenium?

Mohs hardness: 2.0
Brinell hardness: 736 MPa
‣ Young’s modulus of selenium: 10 GPa
‣ Shear modulus of selenium: 3.7 GPa
‣ Bulk modulus of selenium: 8.3 GPa
‣ Selenium CAS number: 7782-49-2

‣ Selenium vapor pressure

Vapor pressure
P (Pa)1101001 k10 k100 k
at T (K)500552617704813958

‣ How many isotopes does selenium have?

Main isotopes of selenium
IsotopeAbundanceHalf-life (t1/2)Decay modeProduct
72Sesyn8.4 dε
γ		72As
–
74Se0.86 %stable
75Sesyn119.8 dε
γ		75As
–
76Se9.23 %stable
77Se7.60 %stable
78Se23.69 %stable
79Setrace3.27 × 105 yβ–79Br
80Se49.80 %stable
82Se8.82 %1.08 × 1020 yβ–β–82Kr

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