Chalcogens, commonly referred to as the Oxygen Group or Group 16, are a group of chemical elements on the periodic table that share distinctive properties because of their valence electron configuration. The term “chalcogen” comes from the Greek word khalkόs, meaning copper, and the Latinized Greek word genēs, meaning born or produced. This refers to the fact that most copper ores are oxides or sulfides. The chalcogen group consists of six elements: oxygen (O), sulfur (S), selenium (Se), tellurium (Te), polonium (Po), and livermorium (Lv). Chalcogens play a vital role in living organisms and industry. Take a closer look at the properties, history, sources, uses, and health effects of these elements.
Their placement in the same element group (column) means these elements share the same valence electron configuration, which gives them similar chemical properties. Their atoms have six electrons in their outermost energy level, giving them a valence of -2, although they exhibit multiple oxidation states.
|16||Sulfur||2, 8, 6|
|34||Selenium||2, 8, 18, 6|
|52||Tellurium||2, 8, 18, 18, 6|
|84||Polonium||2, 8, 18, 32, 18, 6|
|116||Livermorium||2, 8, 18, 32, 32, 18, 6 (predicted)|
Chalcogens are non-metals or metalloids (except possibly livermorium). These elements form various compounds, such as oxides, sulfides, selenides, tellurides, and polonides. They have relatively low melting and boiling points, increasing as you move down the group. Some common properties of chalcogens include:
- Six valence electrons
- High electronegativity, decreasing moving down the group
- Form soft solids
- Poor thermal conductors
- They mainly form covalent bonds with other elements.
- They form both acidic and basic compounds.
- Most chalcogen elements have multiple allotropes. For example, there are at least six forms of oxygen.
Chalcogen Element Facts
- Atomic number: 8
- Symbol: O
- Atomic mass: 15.999 u
- Melting point: -218.79 °C
- Boiling point: -182.95 °C
Oxygen is the third most abundant element in the universe and the most abundant element in the Earth’s crust. This element is essential for respiration and combustion. While a key element for life, oxygen becomes toxic at high concentration levels.
- Atomic number: 16
- Symbol: S
- Atomic mass: 32.066
- Melting point: 115.21 °C
- Boiling point: 444.6 °C
Sulfur occurs in minerals such as gypsum and Epsom salts. It finds use in the production of sulfuric acid and fertilizers. Sulfur is an element that is essential in living organisms, although some of its compounds are toxic.
- Atomic number: 34
- Symbol: Se
- Atomic mass: 78.971
- Melting point: 221 °C
- Boiling point: 685 °C
Selenium occurs in sulfide ores. It is an essential part of some proteins and enzymes and finds use in glass, fertilizers, batteries, and solar cells.
- Atomic number: 52
- Symbol: Te
- Atomic mass: 127.60
- Melting point: 449.51 °C
- Boiling point: 989.8 °C
Tellurium is a rare element, found in the Earth’s crust in only small amounts. It is mildly toxic to humans, although some fungi use it instead of selenium. This element is used in the production of alloys, solar panels, and semiconductors.
- Atomic number: 84
- Symbol: Po
- Atomic mass: 208.982
- Melting point: 254 °C
- Boiling point: 962 °C
Polonium is a highly radioactive and toxic element, with no known biological function. It has use for nuclear reactors and in the production of static eliminators. Polonium occurs as a trace element in uranium ores.
- Atomic number: 116
- Symbol: Lv
- Atomic mass: 
- Melting point: 364–507 °C (extrapolated)
- Boiling point: 762–862 °C (extrapolated)
Livermorium is a synthetic radioactive element. It is so rare and its isotopes decay so rapidly that it often gets excluded from the list of chalcogens. Chemists predict this element is a solid and behaves more as a post-transition metal than as a metalloid. But, it likely has many of the same chemical properties of the other elements in the oxygen group.
History of Discovery
Oxygen was discovered independently by Swedish pharmacist Carl Wilhelm Scheele in 1772 and British chemist Joseph Priestley in 1774. However, it was French chemist Antoine Lavoisier who later named the element “oxygen” in 1777, derived from the Greek words “oxys” (acid) and “genes” (producer).
Sulfur has been known since ancient times, with its discovery dating back to around 2000 BCE. The Chinese, Egyptians, and Greeks were all familiar with sulfur and its properties, using it for various purposes, such as medicines and fumigants.
Selenium was discovered in 1817 by Swedish chemist Jöns Jacob Berzelius. He named the element after the Greek word “selene,” which means “moon.”
Tellurium was discovered in 1782 by Austrian mineralogist and chemist Franz-Joseph Müller von Reichenstein. The element’s name is derived from the Latin word “tellus,” meaning “earth.”
Polonium was discovered in 1898 by Polish physicist and chemist Marie Curie and her husband, Pierre Curie. The element was named after Marie Curie’s homeland, Poland.
Scientists synthesized livermorium at Dubna in 2000. Its name recognizes the achievements of Lawrence Livermore National Laboratory in Livermore, California.
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- Emsley, John (2011). Nature’s Building Blocks: An A-Z Guide to the Elements (New ed.). New York, NY: Oxford University Press. ISBN 978-0-19-960563-7.
- Jensen, William B. (1997). “A Note on the Term “Chalcogen””. Journal of Chemical Education. 74 (9): 1063. doi:10.1021/ed074p1063
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