Se
78.971Selenium
Selenyum
Selenium is a nonmetal with atomic number 34. It is essential in selenoproteins, important in photoconductive materials and thin-film solar cells, and has several allotropes including gray, red and black selenium.
34
78.971 g/mol
[Ar] 3d¹⁰ 4s² 4p⁴
2 | 8 | 18 | 6
2.55
4.809 g/cm³
220.9 °C
684.9 °C
Jöns Jacob Berzelius
Selenium was discovered in 1817 by Jöns Jacob Berzelius while examining residues from sulfuric acid production. It was named after Selene, the Moon, because of its relationship to tellurium, named after Earth.
Selenium-74
Natural abundance: About 0.89%. Stable isotope of selenium.Selenium-76
Natural abundance: About 9.37%. Stable isotope of selenium.Selenium-77
Natural abundance: About 7.63%. Stable isotope used in NMR studies.Selenium-78
Natural abundance: About 23.8%. Stable isotope of selenium.Selenium-80
Natural abundance: About 49.6%. The most abundant stable isotope of selenium.Selenium-82
Natural abundance: About 8.7%. Long-lived isotope studied in double beta decay research.SeO₂
Selenium DioxideUsed in glass chemistry and selective oxidation reactions.H₂Se
Hydrogen SelenideHighly toxic gas and selenium precursor in semiconductor chemistry.Na₂SeO₃
Sodium SeleniteUsed in controlled supplementation and analytical selenium chemistry.SeS₂
Selenium SulfideUsed in some anti-dandruff and antifungal formulations.Cu(In,Ga)Se₂
CIGS AbsorberThin-film solar cell semiconductor material.- Photoconductive materials in historical photocopiers and light sensors
- Glass decolorizing and red or pink glass coloring
- CIGS thin-film solar cells and related semiconductor materials
- Selenium sulfide in some anti-dandruff products
- Dietary and animal feed supplementation in controlled amounts
Selenium is an essential trace element. It occurs in selenocysteine-containing proteins involved in antioxidant defense, thyroid hormone metabolism and redox regulation, but excess selenium can be toxic.
- Selenocysteine is often called the 21st amino acid.
- Gray selenium conducts electricity better when exposed to light.
- The safe intake range for selenium is narrow: both deficiency and excess can be harmful.
- CIGS solar cells rely on selenium-containing semiconductor materials.
- Selenium has atomic number 34 and belongs to group 16, the chalcogens.
- Its electron configuration is [Ar] 3d¹⁰ 4s² 4p⁴.
- Common oxidation states include -2, +4 and +6.
- Selenium is chemically related to sulfur but has stronger metalloid-like and photoconductive behavior in some forms.
What is the atomic number of selenium?
The atomic number of selenium is 34.
What is the electron configuration of selenium?
Selenium has the electron configuration [Ar] 3d¹⁰ 4s² 4p⁴.
Why is selenium important for the body?
Selenium is needed in selenoproteins involved in antioxidant defense, thyroid hormone metabolism and redox regulation.
What are the main allotropes of selenium?
Important selenium allotropes include gray selenium, red selenium and black selenium.
What is selenium used for?
Selenium is used in photoconductive materials, glass chemistry, thin-film solar cells, selenium sulfide products and controlled supplementation.
What is selenocysteine?
Selenocysteine is a selenium-containing amino acid found in the active sites of many selenoproteins.