What is selenium, and what is its symbol and atomic number?

Selenium is a chemical element with the symbol Se and the atomic number 34. It is found in various physical forms, including a brick-red powder, a black vitreous solid, and a gray metallic-looking allotrope.

How did selenium get its name, and who discovered it?

Selenium was discovered in 1817 by the Swedish chemist Jöns Jacob Berzelius. He named it after Selene, the Greek goddess of the moon, due to its similarity to tellurium, which was named after the Earth.

Where is selenium primarily found in nature?

Selenium seldom occurs in its elemental state or as pure ore compounds in the Earth's crust. It is most commonly found as an impurity in metal sulfide ores, where it substitutes for sulfur.

What are the main industrial applications of selenium?

The main commercial uses for selenium are in glassmaking, where it acts as a decolorizer and imparts a red color, and in the production of pigments. It is also utilized as a semiconductor in photocells and certain electronic devices.

Is selenium essential for life, and what are the risks associated with its intake?

Trace amounts of selenium are essential for cellular function in many animals, including humans, as it is a component of important enzymes. However, both elemental selenium and its salts can be toxic in larger doses, leading to a condition known as selenosis.

What are the different allotropes of selenium, and how do they differ?

Selenium exists in several allotropes, which are different structural forms. These include an amorphous, brick-red powder typically formed through chemical reactions, a black vitreous solid formed from rapid melting, and a gray, hexagonal form which is the most stable and dense allotrope. These allotropes interconvert with temperature changes.

Describe the structure and properties of gray selenium.

Gray selenium, the most stable allotrope, possesses a chiral hexagonal crystal lattice composed of helical polymeric chains. It is a semiconductor that exhibits photoconductivity and is insoluble in carbon disulfide, unlike other allotropes. It is also resistant to oxidation by air and non-oxidizing acids.

What are the naturally occurring isotopes of selenium?

Selenium has seven naturally occurring isotopes. Five of these isotopes (74Se, 76Se, 77Se, 78Se, and 80Se) are stable, with 80Se being the most abundant. The isotope 82Se is a primordial radionuclide with a very long half-life, and 79Se occurs in trace amounts as a fission product.

What are the most stable synthetic isotopes of selenium?

Selenium has numerous unstable synthetic isotopes, but the most stable among them are 75Se, with a half-life of approximately 119.78 days, and 72Se, with a half-life of about 8.4 days.

What are the common oxidation states of selenium in its chemical compounds?

Selenium commonly exhibits oxidation states of -2, +2, +4, and +6 in its compounds. It is considered a nonmetal, or sometimes a metalloid, with chemical properties intermediate between sulfur and tellurium.

What are the two oxides of selenium, and how is selenium dioxide formed?

The two oxides of selenium are selenium dioxide (SeO2) and selenium trioxide (SeO3). Selenium dioxide is formed by the combustion of elemental selenium in the presence of oxygen.

What is selenous acid, and how is it prepared?

Selenous acid (H2SeO3) is formed when selenium dioxide dissolves in water. It can also be prepared directly by oxidizing elemental selenium with nitric acid.

How do selenium halides compare to their sulfur counterparts?

Selenium forms halides such as selenium hexafluoride (SeF6), which is more reactive and a greater pulmonary irritant than sulfur hexafluoride (SF6). Selenium also forms stable chlorides like SeCl4 and Se2Cl2, and corresponding bromides, which are structurally similar to their sulfur analogues.

What are metal selenides, and what are some examples?

Metal selenides are compounds formed between selenium and metals. Examples include zinc selenide (ZnSe), lead selenide (PbSe), and mercury selenide (HgSe), many of which function as semiconductors. Hydrogen selenide (H2Se) is a toxic gas analogous to hydrogen sulfide.

What is tetraselenium tetranitride, and how is it synthesized?

Tetraselenium tetranitride (Se4N4) is an explosive orange compound analogous to tetrasulfur tetranitride. It can be synthesized by reacting selenium tetrachloride with specific metal bis(trimethylsilyl)amides.

What are organoselenium compounds, and what are some common examples?

Organoselenium compounds are organic derivatives of selenium, structurally similar to organosulfur compounds. Common examples include selenides (R2Se), diselenides (R2Se2), and selenols (RSeH), such as selenomethionine and benzeneselenol.

When and by whom was selenium discovered?

Selenium was discovered in 1817 by Jöns Jacob Berzelius and Johan Gottlieb Gahn while working at a sulfuric acid plant in Sweden.

What discovery in 1873 led to selenium's use in light-sensing applications?

In 1873, Willoughby Smith discovered that the electrical conductivity of gray selenium was affected by light, leading to its use in devices for sensing light, such as early photocells.

How did selenium's semiconductor properties influence early technology?

Selenium's semiconductor properties, specifically its photoconductivity, were utilized in the development of photocells, light meters, and early solar cells, demonstrating its importance in the nascent field of electronics.

What is the historical significance of selenium rectifiers?

Selenium rectifiers, developed in the early 1930s, were an important application of selenium's semiconductor properties, providing a more efficient alternative to copper oxide rectifiers until they were eventually replaced by silicon-based devices.

How is selenium typically obtained as a byproduct?

Selenium is most commonly obtained as a byproduct during the electrolytic refining of copper, where it is found in the anode mud. It can also be recovered from residues generated during the production of sulfuric acid or from other metal sulfide ores.

Describe the industrial process for producing elemental selenium.

Elemental selenium is typically produced by extracting selenium dioxide from copper refinery residues. This involves oxidizing the residue with sodium carbonate to form selenium dioxide, which is then acidified to create selenous acid. Finally, selenous acid is reduced using sulfur dioxide to yield elemental selenium.

What is the largest commercial use of selenium today?

The largest commercial use of selenium, accounting for approximately 50% of its consumption, is in the production of glass, where it is added to impart a red color and neutralize unwanted tints caused by iron impurities.

What role does selenium play in the human body?

Selenium is an essential trace element in the human body, acting as a cofactor for antioxidant enzymes like glutathione peroxidase and thioredoxin reductase, which help protect cells from oxidative damage. It is also involved in the function of thyroid hormone deiodinases.

What are the potential health effects of selenium deficiency?

Selenium deficiency can occur in individuals with compromised intestinal function or those relying on food from selenium-deficient soils. While pure selenium deficiency is rare, it can be linked to additional stressors like mercury exposure or vitamin E deficiency, potentially affecting immune function and contributing to conditions like Kashin-Beck disease.

What are the symptoms of selenium toxicity (selenosis)?

Symptoms of selenosis, which can occur from excessive selenium intake, include a garlic odor on the breath, gastrointestinal issues, hair loss, nail changes, fatigue, irritability, and neurological damage. In severe cases, it can lead to liver cirrhosis, pulmonary edema, and even death.

How does selenium interact with mercury toxicity?

Increased dietary selenium intake can help mitigate the effects of mercury toxicity, particularly at lower to moderate mercury exposure levels. This is partly because mercury can interfere with selenium-containing enzymes crucial for cellular protection.

What are the primary nutritional sources of selenium?

Dietary sources of selenium include meat, nuts (especially Brazil nuts, which are exceptionally rich), cereals, and mushrooms. The selenium content in plant-based foods is highly dependent on the selenium levels in the soil where they are grown.

What is the recommended daily intake of selenium for adults?

The Recommended Dietary Allowance (RDA) for selenium in the United States for teenagers and adults is 55 micrograms (μg) per day.

What are some examples of selenium pollution incidents?

Notable examples of selenium pollution include the elimination of 15 species of fish from Belews Lake, North Carolina, due to wastewater discharge from a power plant, and the poisoning of thousands of fish and waterbirds at the Kesterson National Wildlife Refuge in California from agricultural irrigation drainage.

What is the role of selenium in thyroid hormone metabolism?

Selenium is a crucial cofactor for three of the four known types of thyroid hormone deiodinases. These enzymes are responsible for activating and deactivating thyroid hormones, playing a vital role in regulating metabolism and energy use in the body.

How is selenium utilized in X-ray detection technology?

Amorphous selenium thin films are used as photoconductors in flat-panel X-ray detectors. They efficiently capture X-ray photons and convert them directly into electric charge, enabling high-quality imaging due to their uniformity and relatively low toxicity compared to other semiconductor materials.

What is the significance of selenium in X-ray crystallography?

In X-ray crystallography, incorporating selenium atoms into protein structures, often replacing sulfur atoms, aids in phasing techniques like Multiple-wavelength Anomalous Dispersion (MAD) and Single Wavelength Anomalous Dispersion (SAD), which are crucial for determining the three-dimensional structure of molecules.

How is selenium used in photography?

Selenium is used in photographic print toning to enhance and extend the tonal range of black-and-white images. It also improves the permanence of photographic prints, making them more resistant to fading over time.

What are some common organoselenium compounds found in living systems?

In living systems, selenium is found incorporated into amino acids such as selenocysteine and selenomethionine, where it functions similarly to sulfur. Dimethyl selenide is another naturally occurring organoselenium compound.

What are the hazards associated with selenium according to the GHS classification?

According to the Globally Harmonized System (GHS), elemental selenium is classified as toxic if swallowed or inhaled (H301+H331), suspected of damaging fertility or the unborn child (H361), causes damage to organs through prolonged or repeated exposure (H372), and may cause long-lasting harmful effects to aquatic life (H413). It carries the signal word 'Danger'.

What is the NFPA 704 rating for selenium?

The NFPA 704 hazard rating for selenium indicates a health hazard of 2 (intense or continued exposure could cause temporary incapacitation or residual injury), flammability of 0 (will not burn), and instability of 0 (normally stable). There is no special hazard code indicated in the white section.

What is the role of selenium in plant nutrition?

Selenium's role in plants varies by species; some require relatively large amounts, while others appear to need none. Certain plants, known as selenium indicators, thrive in selenium-rich soils and can accumulate the element, sometimes as a defense mechanism against herbivores.

What are the main challenges in improving the efficiency of selenium solar cells?

A significant challenge in improving the efficiency of selenium solar cells is the deficit in open-circuit voltage. Strategies like defect engineering in selenium thin films are being investigated to enhance carrier lifetime and overcome this limitation.

What is the significance of the discovery of selenocysteine in proteins?

The discovery of selenocysteine in proteins was significant because it revealed that selenium is directly incorporated into the genetic code via the UGA codon, which typically signals termination but in this case specifies the amino acid selenocysteine.

How does selenium interact with iodine in the context of thyroid health?

Selenium and iodine work together in thyroid health. Selenium acts as a cofactor for deiodinase enzymes, which regulate the activation and deactivation of thyroid hormones, while iodine is a key component of the hormones themselves.

What are some common nutritional sources of selenium, and why is soil content important?

Common nutritional sources of selenium include meat, nuts, cereals, and mushrooms. The selenium content in plant-based foods like Brazil nuts is highly dependent on the selenium levels in the soil, as plants absorb selenium from the soil they grow in.

What is the Tolerable Upper Intake Level (UL) for selenium, and what condition can result from exceeding it?

The Tolerable Upper Intake Level (UL) for selenium for adults is 400 micrograms (μg) per day. Exceeding this level can lead to selenosis, a condition characterized by symptoms such as hair loss, nail brittleness, gastrointestinal issues, and neurological problems.

How does selenium's bioavailability affect its toxicity?

Selenium's bioavailability significantly influences its toxicity. Elemental selenium and metallic selenides have relatively low toxicity due to poor absorption, whereas highly bioavailable forms like selenates and selenites are much more toxic, acting similarly to arsenic compounds.

What are the occupational exposure limits for selenium?

The Occupational Safety and Health Administration (OSHA) has set the permissible exposure limit (PEL) for selenium in the workplace at 0.2 mg/m³ over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has a similar Recommended Exposure Limit (REL).

How can selenium levels be measured in biological samples?

Selenium levels can be measured in biological fluids such as blood, plasma, serum, or urine. These measurements are used to monitor excessive exposure, diagnose poisoning, or assist in forensic investigations.

What is the role of selenium in the immune system?

Research suggests that selenium may play a role in the immune system by acting as an antioxidant and potentially triggering immune responses. It is involved in the creation of selenoproteins, which have antioxidant properties.

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Introduction

Elemental Identity

Selenium, designated by the symbol Se and atomic number 34, is a chemical element exhibiting diverse physical forms, including a brick-red powder, a vitreous black solid, and a grey metallic-like allotrope. It is seldom found in its pure elemental state or as primary ore compounds within the Earth's crust. Its discovery in 1817 by Jöns Jacob Berzelius was prompted by its similarity to tellurium, leading to its naming after the Greek word for the Moon, 'selene'.

Occurrence and Origin

Selenium primarily occurs as a substituent within metal sulfide ores, where it replaces sulfur. Commercially, it is recovered as a byproduct during the refining of these ores. Pure selenide or selenate minerals are notably rare. Its presence in the environment, particularly in soils, can significantly influence plant life, with some species accumulating it to potentially toxic levels.

Scientific Significance

While trace amounts of selenium are vital for cellular functions in many organisms, including humans, both elemental selenium and its salts can exhibit toxicity even at low doses. Its unique semiconductor properties have historically been crucial in electronics and photocells, though silicon has largely superseded it in many applications. Its biological role as a component of essential enzymes underscores its complex nature.

Properties

Allotropes and Appearance

Selenium exists in several allotropic forms that interconvert based on temperature. Chemically prepared selenium typically appears as an amorphous, brick-red powder. When melted and rapidly cooled, it forms a black, vitreous solid. The grey, hexagonal crystalline form is the most stable and dense allotrope, characterized by helical polymeric chains. This grey form exhibits semiconductor properties and notable photoconductivity.

Physical Characteristics

Key physical properties include a melting point of 494 K (220.85 °C) and a boiling point of 958 K (685 °C). The density varies among its allotropes, with the grey form being the densest at 4.81 g/cm³. Selenium exhibits diamagnetism and possesses moderate thermal conductivity. Its mechanical properties, such as Young's modulus and hardness, are characteristic of a brittle nonmetal.

Electronic Behavior

Selenium's status as a semiconductor is central to many of its applications. Its electrical conductivity is sensitive to light (photoconductivity), a property first observed in the grey allotrope. This characteristic paved the way for its use in early photocells and light-sensing devices. The specific band structure and electron mobility contribute to its utility in photoconductive applications like X-ray detectors.

Isotopes

Natural Abundance

Selenium possesses seven naturally occurring isotopes. Five of these—⁷⁴Se, ⁷⁶Se, ⁷⁷Se, ⁷⁸Se, and ⁸⁰Se—are stable. Among these, ⁸⁰Se is the most abundant, constituting approximately 49.6% of natural selenium. The primordial radionuclide ⁸²Se is also naturally present, albeit in trace amounts, with an exceptionally long half-life.

Radioisotopes and Decay

Beyond the stable isotopes, selenium has numerous synthetic radioisotopes, ranging from ⁶⁴Se to ⁹⁵Se. The most significant radioisotope, ⁷⁹Se, has a half-life measured in hundreds of thousands of years and decays via beta-minus emission. ⁷⁵Se, with a half-life of approximately 119.78 days, is also notable. Isotopes lighter than the stable ones typically decay via beta-plus emission, while heavier isotopes undergo beta-minus decay.

Isotope	Abundance (%)	Half-life	Decay Mode	Product
⁷⁴Se	0.86	Stable	-	-
⁷⁶Se	9.23	Stable	-	-
⁷⁷Se	7.60	Stable	-	-
⁷⁸Se	23.7	Stable	-	-
⁷⁹Se	Trace	3.27×10⁵ y	β^-	⁷⁹Br
⁸⁰Se	49.8	Stable	-	-
⁸²Se	8.82	8.76×10¹⁹ y	2β^-	⁸²Kr

Compounds

Oxidation States and Analogies

Selenium commonly exhibits oxidation states of -2, +2, +4, and +6. As a nonmetal, bordering on metalloid, its chemical behavior is intermediate between sulfur and tellurium, sharing similarities with arsenic. This positions it uniquely within the chalcogen group.

Oxides and Acids

Selenium forms two primary oxides: selenium dioxide (SeO₂) and the less stable selenium trioxide (SeO₃). Combustion of elemental selenium yields SeO₂, which dissolves in water to form selenous acid (H₂SeO₃). Selenous acid can also be synthesized directly. Selenium trioxide decomposes readily into the dioxide and oxygen above 185 °C.

Halides and Selenides

Stable selenium halides include selenium tetrachloride (SeCl₄) and selenium monochloride (Se₂Cl₂), analogous to their sulfur counterparts. Selenium hexafluoride (SeF₆) is more reactive and toxic than sulfur hexafluoride. Selenium readily forms selenides with metals, such as zinc selenide (ZnSe) and lead selenide (PbSe), which are important semiconductors. It also forms polyselenides, characterized by chains of selenium atoms.

Organoselenium Chemistry

Selenium forms a variety of organoselenium compounds analogous to organosulfur compounds. These include selenides (R₂Se), diselenides (R₂Se₂), and selenols (RSeH). Notably, selenocysteine and selenomethionine are biologically significant amino acids containing selenium. However, compounds like selenoketones are rarely observed due to chemical principles related to double bond stability.

History

Discovery and Naming

Discovered in 1817 by Jöns Jacob Berzelius and Johan Gottlieb Gahn during their work with sulfuric acid production, selenium's unique properties, including a distinct odor reminiscent of tellurium compounds, led Berzelius to name it after the Moon ('selene' in Greek), reflecting its connection to tellurium (named for Earth).

Early Applications

Willoughby Smith's 1873 discovery of selenium's photoconductivity marked a significant milestone. This property enabled its use in early light-sensing devices, such as Alexander Graham Bell's photophone. Selenium rectifiers, developed in the 1930s, were important electronic components until largely replaced by silicon devices.

Biological Recognition

Selenium's biological significance emerged later. Initial observations in microorganisms in 1954 hinted at its essentiality, which was confirmed for mammalian life in 1957. Subsequent research identified selenium as a crucial component of vital enzymes like glutathione peroxidase and thioredoxin reductase, and its role in thyroid hormone metabolism was elucidated.

Occurrence

Geological Presence

Native selenium is a rare mineral, typically found in small, acicular crystals. Its isolation is often complicated by its association with other elements. Selenium is most commonly found as a trace impurity, substituting for sulfur in various metal sulfide ores. Minerals containing pure selenide or selenate are uncommon.

Biological Systems

In living organisms, selenium is incorporated into amino acids such as selenocysteine and selenomethionine, analogous to sulfur's role. Certain plants act as indicators of selenium-rich soils, accumulating the element, sometimes to levels toxic to grazing animals. Ocean water also contains significant concentrations of selenium.

Environmental Distribution

Typical background concentrations in the atmosphere, soil, and water are generally low. However, anthropogenic activities, including coal combustion and the mining and smelting of sulfide ores, contribute to environmental selenium levels. Soluble forms like selenate can leach into waterways, potentially causing pollution issues.

Production

Primary Sources

The principal source of commercial selenium is its recovery as a byproduct from the refining of sulfide ores, particularly those of copper, nickel, and lead. Electrolytic copper refining yields significant amounts of selenium from anode muds. Historically, sulfuric acid production also yielded selenium from lead chamber process residues.

Refining Processes

Industrial production typically involves extracting selenium dioxide from copper refinery residues. This is often achieved through oxidation with sodium carbonate, followed by acidification to form selenous acid. Subsequent reduction of selenous acid, commonly using sulfur dioxide, precipitates elemental selenium.

Global Output

Global selenium production is concentrated in specific countries, with Germany, Japan, Belgium, and Russia being major producers. Consumption patterns vary, with significant use in metallurgy, glass manufacturing, agriculture, and electronics. China stands out as a dominant consumer, particularly for manganese electrolysis applications.

Applications

Glass and Pigments

The largest commercial application of selenium is in glass manufacturing, where its compounds impart a red color, effectively neutralizing green tints caused by iron impurities. Selenium compounds are also used to produce vibrant red pigments.

Metallurgy and Alloys

Selenium enhances the machinability of steel and copper alloys, similar to lead and sulfur. It is also used in brass alloys (e.g., EnviroBrass) as a less toxic alternative to lead, particularly in applications related to drinking water systems.

Electronics and Energy

Historically vital for photocells, light meters, and early solar cells, selenium's photoconductive properties remain relevant in modern X-ray detectors. While silicon has largely replaced it in solar cells, research continues into selenium-based tandem cells. Selenium rectifiers still find niche use in surge protection.

Emerging Technologies

Lithium-selenium batteries have been explored for energy storage applications. Furthermore, cadmium selenide (CdSe) is utilized in the production of quantum dots, highlighting selenium's role in advanced materials science.

Biological Role

Essential Micronutrient

Selenium is an essential trace element for animal life, functioning as a critical cofactor for antioxidant enzymes such as glutathione peroxidases and thioredoxin reductases. These enzymes play vital roles in cellular redox balance and protection against oxidative damage.

Thyroid Function

In conjunction with iodine, selenium is integral to thyroid health. It serves as a cofactor for deiodinase enzymes, which regulate the activation and inactivation of thyroid hormones. Selenium deficiency, particularly when combined with other stressors, is being investigated for its potential link to thyroid disorders like Hashimoto's disease.

Nutritional Sources

Dietary selenium is obtained from sources like meat, nuts (especially Brazil nuts, which are exceptionally rich), cereals, and mushrooms. The Recommended Dietary Allowance (RDA) for adults is 55 micrograms per day. Selenium is available in various supplement forms, including multivitamins.

Toxicity

Selenosis and Symptoms

Ingestion of excessive selenium, particularly from highly bioavailable forms like selenates and selenites, can lead to selenosis. Symptoms range from garlic breath, gastrointestinal issues, hair loss, and nail changes to neurological damage and, in severe cases, liver cirrhosis or pulmonary edema. The Tolerable Upper Intake Level is established at 400 micrograms per day.

Hazard Classification

Under the Globally Harmonized System (GHS), elemental selenium is classified as toxic if swallowed or inhaled (H301+H331), suspected of damaging fertility or the unborn child (H361), and causing damage to organs through prolonged or repeated exposure (H372). It may also cause long-lasting harmful effects to aquatic life (H413).

Occupational Exposure

Occupational Safety and Health Administration (OSHA) has set permissible exposure limits for selenium in the workplace. Prolonged exposure to airborne selenium dust or fumes requires careful monitoring and control measures to prevent adverse health effects.

Pollution

Sources of Contamination

Selenium pollution can arise from agricultural runoff, particularly in arid regions where soluble selenium compounds leach into waterways. Industrial processes, including coal combustion, mining, smelting, and crude oil processing, also contribute to environmental selenium levels.

Aquatic Ecosystem Impacts

Elevated selenium concentrations in aquatic environments can be detrimental, causing developmental abnormalities and mortality in fish and waterbirds. Bioaccumulation occurs along the food chain, leading to significantly higher concentrations in organisms than in the surrounding water. Certain thresholds are considered highly hazardous to aquatic life.

Health Implications

While fish consumption is generally beneficial, high selenium levels in fish can pose risks. Selenium poisoning can lead to physiological changes in fish, including respiratory impairment and reproductive issues. The interaction between selenium and methylmercury can amplify toxicity in aquatic species.

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References

http://weppi.gtk.fi/publ/foregsatlas/text/Se.pdf

R. Baselt, Disposition of Toxic Drugs and Chemicals in Man, 8th edition, Biomedical Publications, Foster City, CA, 2008, pp. 1416â1420.

A full list of references for this article are available at the Selenium Wikipedia page

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This document was generated by an AI model and is intended for educational and informational purposes only. The content is derived from publicly available data and has been refined for clarity and academic tone, suitable for higher education students. While efforts have been made to ensure accuracy based on the provided source material, completeness and current applicability cannot be guaranteed.

This is not professional advice. The information presented here does not constitute chemical, medical, or safety consultation. Users should consult official documentation and qualified professionals for any specific applications or concerns related to selenium, including its handling, toxicity, and biological interactions. Reliance on the information provided herein is solely at the user's own risk.

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Selenium: The Lunar Element Unveiled

💡 Dive in with Flashcard Learning! 💡

Introduction ℹ️

⚛️ Elemental Identity

🌍 Occurrence and Origin

🔬 Scientific Significance

Properties ⚙️

🌈 Allotropes and Appearance

⚡ Physical Characteristics

💡 Electronic Behavior

Isotopes 🎛️

🌿 Natural Abundance

☢️ Radioisotopes and Decay

Compounds 🧪

🌐 Oxidation States and Analogies

🔥 Oxides and Acids

🔗 Halides and Selenides

🌿 Organoselenium Chemistry

History 📜

🌙 Discovery and Naming

💡 Early Applications

🔬 Biological Recognition

Occurrence 📍

⛰️ Geological Presence

🌱 Biological Systems

🏭 Environmental Distribution

Production 🏭

⛏️ Primary Sources

🧪 Refining Processes

📊 Global Output

Applications 💡

🖼️ Glass and Pigments

🔗 Metallurgy and Alloys

☀️ Electronics and Energy

🔋 Emerging Technologies

Biological Role 🌿

🧬 Essential Micronutrient

⚙️ Thyroid Function

🍽️ Nutritional Sources

Toxicity ⚠️

☠️ Selenosis and Symptoms

GHS Hazard Classification

🏢 Occupational Exposure

Pollution 🌊

🏭 Sources of Contamination

🐟 Aquatic Ecosystem Impacts

⚠️ Health Implications

Teacher's Corner 🧑‍🏫

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References

📜 References

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Disclaimer ⚠️

📜 Important Notice

Dive in with Flashcard Learning!

Introduction

Elemental Identity

Occurrence and Origin

Scientific Significance

Properties

Allotropes and Appearance

Physical Characteristics

Electronic Behavior

Isotopes

Natural Abundance

Radioisotopes and Decay

Compounds

Oxidation States and Analogies

Oxides and Acids

Halides and Selenides

Organoselenium Chemistry

History

Discovery and Naming

Early Applications

Biological Recognition

Occurrence

Geological Presence

Biological Systems

Environmental Distribution

Production

Primary Sources

Refining Processes

Global Output

Applications

Glass and Pigments

Metallurgy and Alloys

Electronics and Energy

Emerging Technologies

Biological Role

Essential Micronutrient

Thyroid Function

Nutritional Sources

Toxicity

Selenosis and Symptoms

Hazard Classification

Occupational Exposure

Pollution

Sources of Contamination

Aquatic Ecosystem Impacts

Health Implications

Teacher's Corner

True or False?

Test Your Knowledge!

Gamer's Corner

Discover other topics to study!

References

Feedback & Support

Disclaimer

Important Notice