Selenium

Selenium
Selenium block | Image: Learnool

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.

On periodic table

group 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
period
1 1
H
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Hydrogen
2
He
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Helium
2 3
Li
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Lithium
4
Be
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Beryllium
5
B
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Boron
6
C
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Carbon
7
N
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Nitrogen
8
O
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Oxygen
9
F
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Fluorine
10
Ne
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Neon
3 11
Na
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Sodium
12
Mg
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Magnesium
13
Al
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Aluminium
14
Si
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Silicon
15
P
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Phosphorus
16
S
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Sulfur
17
Cl
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Chlorine
18
Ar
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Argon
4 19
K
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Potassium
20
Ca
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Calcium
21
Sc
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Scandium
22
Ti
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Titanium
23
V
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Vanadium
24
Cr
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Chromium
25
Mn
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Manganese
26
Fe
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Iron
27
Co
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Cobalt
28
Ni
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Nickel
29
Cu
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Copper
30
Zn
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Zinc
31
Ga
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Gallium
32
Ge
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Germanium
33
As
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Arsenic
34
Se
Selenium
35
Br
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Bromine
36
Kr
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Krypton
5 37
Rb
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Rubidium
38
Sr
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Strontium
39
Y
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Yttrium
40
Zr
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Zirconium
41
Nb
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Niobium
42
Mo
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Molybdenum
43
Tc
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Technetium
44
Ru
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Ruthenium
45
Rh
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Rhodium
46
Pd
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Palladium
47
Ag
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Silver
48
Cd
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Cadmium
49
In
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Indium
50
Sn
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Tin
51
Sb
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Antimony
52
Te
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Tellurium
53
I
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Iodine
54
Xe
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Xenon
6 55
Cs
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Caesium
56
Ba
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Barium
72
Hf
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Hafnium
73
Ta
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Tantalum
74
W
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Tungsten
75
Re
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Rhenium
76
Os
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Osmium
77
Ir
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Iridium
78
Pt
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Platinum
79
Au
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Gold
80
Hg
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Mercury
81
Tl
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Thallium
82
Pb
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Lead
83
Bi
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Bismuth
84
Po
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Polonium
85
At
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Astatine
86
Rn
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Radon
7 87
Fr
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Francium
88
Ra
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Radium
104
Rf
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Rutherfordium
105
Db
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Dubnium
106
Sg
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Seaborgium
107
Bh
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Bohrium
108
Hs
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Hassium
109
Mt
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Meitnerium
110
Ds
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Darmstadtium
111
Rg
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Roentgenium
112
Cn
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Copernicium
113
Nh
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Nihonium
114
Fl
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Flerovium
115
Mc
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Moscovium
116
Lv
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Livermorium
117
Ts
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Tennessine
118
Og
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Oganesson
57
La
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Lanthanum
58
Ce
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Cerium
59
Pr
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Praseodymium
60
Nd
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Neodymium
61
Pm
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Promethium
62
Sm
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Samarium
63
Eu
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Europium
64
Gd
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Gadolinium
65
Tb
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Terbium
66
Dy
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Dysprosium
67
Ho
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Holmium
68
Er
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Erbium
69
Tm
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Thulium
70
Yb
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Ytterbium
71
Lu
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Lutetium
89
Ac
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Actinium
90
Th
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Thorium
91
Pa
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Protactinium
92
U
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Uranium
93
Np
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Neptunium
94
Pu
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Plutonium
95
Am
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Americium
96
Cm
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Curium
97
Bk
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Berkelium
98
Cf
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Californium
99
Es
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Einsteinium
100
Fm
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Fermium
101
Md
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Mendelevium
102
No
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Nobelium
103
Lr
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Lawrencium
– p block

Selenium is a p-block element, situated in the sixteenth column and the fourth row of the periodic table. Its atomic number is 34 and its symbol is Se.

Element information

Selenium Element
Selenium appearance | Image: Wikipedia
Selenium Periodic Table
Selenium location on periodic table | Image: Learnool
Selenium is found in the fourth row of the periodic table below the sulfur element.
Origin of name Greek word “selene” (which means Moon)
Symbol Se
Atomic number (Z) 34
Atomic mass 78.96 u
Block p-block
Group 16 (oxygen group)
Period 4
Classification Reactive nonmetal
Atomic radius 120 pm
Covalent radius 120±4 pm
Van der Waals radius 190 pm
Melting point 221 ℃, 430 ℉, 494 K
Boiling point 685 ℃, 1265 ℉, 958 K
Electron configuration [Ar] 3d10 4s2 4p4
Learn how to write: Selenium electron configuration
Electrons per shell 2, 8, 18, 6
Learn how to draw: Selenium Bohr model
Crystal structure Trigonal
Phase at r.t Solid
Density near r.t Gray: 4.81 g/cm3
Alpha: 4.39 g/cm3
Vitreous: 4.28 g/cm3
Main isotopes Selenium-74, Selenium-76, Selenium-77, Selenium-78, Selenium-80
Natural occurrence Primordial
Oxidation state -2, +2, +4, +6
Electronegativity (Pauling scale) 2.55
Protons
Neutrons
Electrons
34
45
34
Learn how to find: Selenium protons neutrons electrons
Valence electrons 6
Learn how to find: Selenium valence electrons
CAS number 7782-49-2
Discovered by Jöns Jacob Berzelius and Johann Gottlieb Gahn in 1817

History

Selenium, derived from the Greek word “selene,” meaning Moon, was discovered in 1817 by Swedish chemists Jöns Jacob Berzelius and Johan Gottlieb Gahn. They found a red precipitate in the lead chambers of their chemistry plant near Gripsholm, which was later identified as a new element similar to sulfur and tellurium. Initially, Berzelius thought it was a tellurium compound due to its smell, but he eventually reanalyzed it and named it selenium after the Moon because of its similarity to tellurium, named after the Earth.

In the mid-1870s, Werner Siemens developed the first commercial products using selenium. Willoughby Smith found that the electrical resistance of grey selenium was affected by ambient light, leading to its use as a cell for sensing light. Alexander Graham Bell used selenium in his photophone in 1879. Selenium’s semiconductor properties found numerous applications in electronics, including the development of selenium rectifiers in the 1930s.

Selenium’s toxic effects on industrial workers and animals eating high-selenium plants were discovered later. Biochemist Jane Pinsent discovered its importance in microorganisms in 1954, and it was found to be essential for mammalian life in 1957. Selenocysteine, a component of proteins, was discovered in the 1980s, and it was shown to be encoded by the codon UGA. The recoding mechanism was first worked out in bacteria and then in mammals. Today, selenium is recognized as a crucial micronutrient for human and animal health.

Occurrence

Selenium is a nonmetal that occurs naturally in the Earth’s crust, typically found in minerals such as selenite, selenate, and selenide. It is widely distributed in rocks and soils, but its concentration varies depending on the location.

Selenium is present in small amounts in the human body and is necessary for the proper functioning of several enzymes. It is also an essential nutrient for animals, with a deficiency leading to health problems such as muscle weakness, hair loss, and immune system dysfunction.

The largest known reserves of selenium are in the United States, with significant deposits also found in Canada, China, Russia, and Peru. Other sources of selenium include coal, crude oil, and natural gas. However, the concentration of selenium in these sources can vary widely, and it is often necessary to extract it using chemical methods.

Production

Selenium is commonly produced from selenide found in sulfide ores, such as copper, nickel, or lead. Electrolytic metal refining is a major source of selenium as a byproduct, obtained from the anode mud of copper refineries. Industrial production of selenium usually involves the extraction of selenium dioxide from residues obtained during the purification of copper. Common production from the residue begins with oxidation using sodium carbonate to produce selenium dioxide, which is mixed with water and acidified to form selenous acid. Selenous acid is then bubbled with sulfur dioxide to give elemental selenium.

In 2011, approximately 2,000 tonnes of selenium were produced worldwide, with Germany, Japan, Belgium, and Russia being the largest producers. The total reserves of selenium were estimated at 93,000 tonnes. The consumption of selenium in 2010 was mainly for metallurgy, glass manufacturing, agriculture, and chemicals and pigments. China is the dominant consumer of selenium, consuming 1,500 to 2,000 tonnes per year.

Properties

Selenium has a grey crystalline appearance and is a brittle nonmetal with some reactive and semiconducting properties.

It has a melting point of 221 degrees Celsius and a boiling point of 685 degrees Celsius.

Selenium is a chalcogen, which means it belongs to the same group as oxygen, sulfur, and tellurium in the periodic table.

It is insoluble in water but is soluble in chloroform, carbon disulfide, and other organic solvents.

Selenium has six stable isotopes, with the two most abundant ones being selenium-80 and selenium-78.

Selenium is a photoconductive material, which means that its electrical conductivity increases when exposed to light.

It is also an essential trace element for humans and animals and is found in small amounts in various foods.

Selenium exhibits different oxidation states, ranging from -2 to +6, with -2, +4, and +6 being the most common.

Selenium has many unique properties, including its ability to form glasses, its use in solar cells, and its role in the production of certain pigments and dyes.

Applications

Photovoltaic cells

Selenium is a key component of thin-film photovoltaic cells. It is used as a semiconductor material in these cells, which convert sunlight into electricity. This makes it an important element in the field of solar energy.

Glass industry

Selenium compounds are used as coloring agents in the glass industry. It can produce colors ranging from red to yellow to gray in glass, making it useful in the manufacture of tinted glass, colored glassware, and mirrors.

Pharmaceuticals

Selenium is used in the pharmaceutical industry for various purposes. It is used as a nutritional supplement in medicines, as it has antioxidant properties. It is also used in the treatment of dandruff, seborrheic dermatitis, and other skin diseases.

Agriculture

Selenium is an essential micronutrient for plants and animals. It is used as a fertilizer in agriculture to improve crop yield and quality. Selenium-enriched fertilizers are used to grow crops that are rich in this micronutrient.

Rubber industry

Selenium compounds are used as vulcanizing agents in the rubber industry. They help to improve the mechanical properties of rubber, such as elasticity, tensile strength, and abrasion resistance.

Electronics

Selenium is used in electronic devices such as photocopiers and printers. It is used as a photosensitive material in these devices, which convert light into electrical signals.

Interesting facts

Selenium was named after the Greek word “Selene,” meaning Moon, by the Swedish chemist Jöns Jacob Berzelius in 1817 due to its similar properties to tellurium, which was named after the Latin word for Earth.

Selenium is the key component in many toners, which are used in the production of photocopying machines, printers, and other electronic devices.

Ingesting too much selenium can lead to a condition called selenosis, which can cause hair and nail loss, skin lesions, and other health problems.

Selenium is a trace element found in the Earth’s crust, comprising only about 90 parts per billion.

Selenium has a number of beneficial effects on human health, including acting as an antioxidant and supporting thyroid function.

Some plants, such as broccoli and garlic, are good sources of selenium, while others, such as rice grown in certain parts of the world, can be high in selenium due to the soil conditions.

Selenium has been used in the glass industry to decolorize glass and to create a red color in stained glass.

Selenium is also used in the manufacturing of rubber products, such as tires, to improve their durability and resistance to heat.

Selenium is a semiconducting material, which makes it useful in the production of photovoltaic cells used in solar panels.

Related

More elements

s block
p block
d block
f block
Barium Aluminium Bohrium Actinium
Beryllium Antimony Cadmium Americium
Caesium Argon Chromium Berkelium
Calcium Arsenic Cobalt Californium
Francium Astatine Copernicium Cerium
Helium Bismuth Copper Curium
Hydrogen Boron Darmstadtium Dysprosium
Lithium Bromine Dubnium Einsteinium
Magnesium Carbon Gold Erbium
Potassium Chlorine Hafnium Europium
Radium Flerovium Hassium Fermium
Rubidium Fluorine Iridium Gadolinium
Sodium Gallium Iron Holmium
Strontium Germanium Lawrencium Lanthanum
Indium Lutetium Mendelevium
Iodine Manganese Neodymium
Krypton Meitnerium Neptunium
Lead Mercury Nobelium
Livermorium Molybdenum Plutonium
Moscovium Nickel Praseodymium
Neon Niobium Promethium
Nihonium Osmium Protactinium
Nitrogen Palladium Samarium
Oganesson Platinum Terbium
Oxygen Rhenium Thorium
Phosphorus Rhodium Thulium
Polonium Roentgenium Uranium
Radon Ruthenium Ytterbium
Selenium Rutherfordium
Silicon Scandium
Sulfur Seaborgium
Tellurium Silver
Tennessine Tantalum
Thallium Technetium
Tin Titanium
Xenon Tungsten
Vanadium
Yttrium
Zinc
Zirconium

External links

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Learnool.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.

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