Selenium

Some things are named after the moon.

This is one of them. A scientist found it in 1817. He named it after the moon goddess.

It can look many ways. It can be a red powder. It can be a black solid. It can even look like gray metal.

People use it to make glass. They also use it to make colors. It can help make some vitamins, too.

Small amounts are good for animals. But too much can make them sick. This can cause hair loss or pain.

It is a very useful thing. We find it in the ground near other metals.

Selenium is a chemical element. It has the symbol Se.

Two scientists found it in 1817. They named it after Selene. Selene is the Greek goddess of the moon.

They named it this because it is like tellurium. Tellurium is named after the Earth.

Selenium can look many ways. It can be a red powder. It can be a black solid. It can also look like gray metal.

The gray form is a semiconductor. A semiconductor is a material that can carry electricity. This helps it work in electronics. People use it in glassmaking and for pigments.

Many animals need tiny amounts of selenium. It helps their cells work. It is even found in many vitamins. But too much selenium is toxic. This means it can be poisonous. It can cause hair loss or joint pain.

Selenium dioxide is a solid made from selenium. It can dissolve in water. Selenium is often found in metal ores. It is a byproduct of making those metals.

Selenium is a chemical element with the symbol Se and atomic number 34. It is a fascinating substance because it can take on many different shapes. It can appear as a brick-red powder or a shiny, grey metallic form. It can also look like a black, glass-like solid.

Most of the time, you will not find pure selenium just sitting in the Earth's crust. Instead, it is usually found inside metal sulfide ores. In these ores, selenium often takes the place of sulfur. Because of this, companies often find selenium as a byproduct while they are refining other metals.

This element works in many interesting ways depending on its form. The grey form is a semiconductor, which means it can carry electricity under certain conditions. This makes it very useful for making photocells. While silicon is now used more often for electronics, selenium is still used in some power surge protectors.

When selenium is heated, it can change its shape. For example, black selenium softens at 50 °C. If you heat it more to 180 °C, it turns into grey selenium. This happens because the atoms rearrange themselves into new patterns. The black form even has very large rings made of up to 1000 atoms.

Two scientists discovered selenium in 1817. Their names were Jöns Jacob Berzelius and Johan Gottlieb Gahn. They worked at a chemistry plant near Gripsholm, Sweden.

They were studying pyrite samples from the Falun Mine. They noticed a red solid that smelled like horseradish when burned. This smell reminded them of tellurium. Since tellurium was named after the Earth, they decided to name selenium after the Moon. They chose this name because of the Greek goddess Selene. This was a clever way to show how the two elements are related.

There are many specific facts about how selenium behaves. It has seven naturally occurring isotopes, which are different versions of the element. The most common one is 80Se, which makes up 49.6% of all natural selenium.

Selenium can also form different compounds like selenium dioxide. When selenium dioxide dissolves in water, it creates selenous acid. Some selenium compounds, like selenium disulfide, are even used in shampoos to fight dandruff. Other types, like selenium hexafluoride, are very reactive and can be irritating to breathe.

Even though it has many uses, selenium is something we must handle with care. Many living things, including humans, need tiny amounts of selenium to help their cells work. It is often added to multivitamins and infant formula to keep us healthy. However, too much selenium is toxic and can cause selenosis. This sickness can lead to hair loss, fatigue, or joint pain.

It is a great example of how a single element can be both helpful and dangerous depending on how much is used.

Selenium is a chemical element with the symbol Se and atomic number 34. It is a versatile substance that can exist in many different physical forms. These forms are known as allotropes, which are different structural arrangements of the same atoms. Selenium can appear as a brick-red powder, a black vitreous solid, or a grey metallic-looking form.

It is classified as a nonmetal or sometimes a metalloid. This means its properties sit between those of metals and nonmetals. It shows similarities to the elements sulfur and tellurium, as well as arsenic. Because of these unique traits, selenium plays vital roles in both biology and technology.

Understanding how selenium changes requires looking at its molecular structure. When selenium is prepared through chemical reactions, it usually forms an amorphous, brick-red powder. If this substance is melted rapidly, it becomes a black, vitreous solid. This black form is brittle and lustrous. Its structure is quite complex, consisting of polymeric rings that can contain up to 1000 atoms.

Temperature plays a major role in how these shapes shift. Black selenium softens at 50 °C. If you continue heating it to 180 °C, it converts into grey selenium. The presence of certain chemicals, like halogens or amines, can actually lower the temperature needed for this change.

Gray selenium is the most stable and dense version of the element. Unlike the other forms, gray selenium is a semiconductor. A semiconductor is a material that can conduct electricity under specific conditions. This makes it highly photoconductive, meaning it responds to light. In this state, the atoms form helical polymeric chains in a hexagonal crystal lattice. The distance between the selenium atoms in these chains averages 237.3 pm.

This specific arrangement allows it to resist oxidation by air and withstand nonoxidizing acids.

The discovery of selenium is a famous story in chemistry. In 1817, scientists Jöns Jacob Berzelius and Johan Gottlieb Gahn were working near Gripsholm, Sweden. They were using pyrite samples from the Falun Mine to produce sulfuric acid. They noticed a red solid precipitate that smelled like horseradish when burned. At first, they thought it was an arsenic compound. However, the smell reminded them of tellurium.

Because tellurium was named after the Earth, Berzelius decided to name this new element after the Moon. He chose the name selenium, which comes from Selene, the Greek goddess of the Moon.

Selenium is found in nature in several different forms, known as isotopes. There are seven naturally occurring isotopes of selenium. The most abundant is 80Se, which makes up 49.6% of all natural selenium.

There is also a long-lived primordial radionuclide called 82Se. It has a massive half-life of 8.76×10^19 years. Other isotopes, like 79Se, appear in tiny amounts in uranium ores due to nuclear fission. In a laboratory, scientists can create unstable synthetic isotopes. These range from 64Se to 95Se, with some lasting only a few days.

In the modern world, selenium has many important commercial uses. It is a byproduct of refining metal sulfide ores, where it often substitutes for sulfur. Today, it is used heavily in glassmaking and the production of pigments. Because it is a semiconductor, it was once very important in electronics. While silicon has mostly replaced it in many devices, selenium is still used in certain DC power surge protectors. It is also used in one type of fluorescent quantum dot.

Some of its compounds, like selenium disulfide, are used in shampoos to treat dandruff.

Biology shows us that selenium is a delicate balance for living things. Many animals and humans require trace amounts of selenium for cellular function. It is a key component in important antioxidant enzymes. These include glutathione peroxidase, thioredoxin reductase, and three different deiodinase enzymes. Because it is so necessary, it is added to infant formula and many multivitamins. However, too much selenium is dangerous. Even small doses of elemental selenium or its salts can be toxic. This toxicity causes a condition called selenosis. Symptoms can include fatigue, hair loss, joint pain, and nail discoloration.