selenium

Also known as Se, element 34, 34Se

Selenium is a chemical element; it has symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elemental state or as pure ore compounds in Earth's crust. Selenium (from ) was discovered in 1817 by , who noted the similarity of the new element to the previously discovered tellurium (named for the Earth).

OverviewAI-generated

Selenium is a chemical element with the symbol Se and atomic number 34. Its standard chemical formula is Se, and it has a mass of 78.971. The element was discovered in 1817. It exhibits oxidation states of -2, 1, 2, and 4, and has an electronegativity of 2.55. The ionic radius is 0.50.

Physical properties include a density of 4.28, a melting point of 392, and a boiling point of 1265. The vapor pressure is 0. Safety guidelines list a time-weighted average exposure limit of 0.2 and an immediately dangerous to life or health value of 1. The NIOSH Pocket Guide ID is 0550. In digital text, it is represented by the Unicode character "硒".

Synthesized by Vinony from 31 facts across 4 sources: Wikidata, PubChem, PubMed, Vinony graph. Generated from structured data (not the Wikipedia text) and checked against those facts — may still contain errors.

Chemical data

Formula: Se
Molecular weight: 78.97 g/mol
IUPAC name: selenium
SMILES: [Se]
InChIKey: BUGBHKTXTAQXES-UHFFFAOYSA-N
Polar surface area: 0 Å²
H-bond donors: 0
H-bond acceptors: 0
Formal charge: 0

via PubChem

Research

50,303 papers

Effects and Impact of Selenium on Human Health, A Review.ReviewMolecules (Basel, Switzerland) · 2024Bai S, Zhang M, Tang S et al.DOI: 10.3390/molecules30010050
Selenium.ReviewJournal of toxicology. Clinical toxicology · 1999Barceloux DGDOI: 10.1081/clt-100102417
Selenium-More than Just a Fortuitous Sulfur Substitute in Redox Biology.ReviewMolecules (Basel, Switzerland) · 2023Maia LB, Maiti BK, Moura I et al.DOI: 10.3390/molecules29010120
Selenium Biofortification: A Dual-Edged Sword of Nutrition and Contamination Risk.ReviewComprehensive reviews in food science and food safety · 2025Xi Z, Chen C, Zhu D et al.DOI: 10.1111/1541-4337.70345
Selenium and brain aging: A comprehensive review with a focus on hippocampal neurogenesis.ReviewAgeing research reviews · 2025Daneshpour A, Leite MEN, Wagner KH et al.DOI: 10.1016/j.arr.2025.102898
Research Progress of Selenium-Enriched Foods.ReviewNutrients · 2023Chen Z, Lu Y, Dun X et al.DOI: 10.3390/nu15194189
Selenium action in neuro-oncology.ReviewBiological trace element research · 2014Yakubov E, Buchfelder M, Eyüpoglu IY et al.DOI: 10.1007/s12011-014-0111-8
Selenium.ReviewJournal of dairy science · 1970Hogue DEDOI: 10.3168/jds.S0022-0302(70)86356-1

via PubMed

~32 min read

Encyclopedic overview

33 sections

Contents

Characteristics
Physical properties
Isotopes
Chemical compounds
Chalcogen compounds
Halogen compounds
Metal selenides
Other compounds
Organoselenium compounds
History
Occurrence
Production
Applications
Manganese electrolysis
Glass production
Alloys
Lithium–selenium batteries
Solar cells
Photoconductors
Rectifiers
Other uses
Pollution
Examples
Biological role
Nutritional sources of selenium
Toxicity
Detection in biological fluids
Deficiency
General health effects
See also
Notes
References
External links

Selenium is found in metal sulfide ores, where it substitutes for sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores. Minerals that are pure selenide or selenate compounds are rare. The chief commercial uses for selenium today are glassmaking and pigments. Selenium is a semiconductor and is used in photocells. Applications in electronics, once important, have been mostly replaced with silicon semiconductor devices. Selenium is still used in a few types of DC power surge protectors and one type of fluorescent quantum dot.

Excerpted from Wikipedia’s “selenium” article, available under the CC BY-SA 4.0 licence.