![]() ![]() Oxygen is generally obtained by separation of air into nitrogen and oxygen. This trend also occurs with chalcogen pnictides and compounds containing chalcogens and carbon group elements. Not counting oxygen, organic sulfur compounds are generally the most common, followed by organic selenium compounds and organic tellurium compounds. There are numerous organic chalcogen compounds. Sulfur has more than 20 allotropes, oxygen has nine, selenium has at least eight, polonium has two, and only one crystal structure of tellurium has so far been discovered. Tellurium often has unpleasant effects (although some organisms can use it), and polonium (especially the isotope polonium-210) is always harmful as a result of its radioactivity. Selenium is an important nutrient (among others as a building block of selenocysteine) but is also commonly toxic. Īll of the naturally occurring chalcogens have some role in biological functions, either as a nutrient or a toxin. They have relatively low atomic radii, especially the lighter ones. Their most common oxidation states are −2, +2, +4, and +6. All of the chalcogens have six valence electrons, leaving them two electrons short of a full outer shell. Selenium, tellurium and polonium were discovered in the 19th century, and livermorium in 2000. Sulfur has been known since antiquity, and oxygen was recognized as an element in the 18th century. The word "chalcogen" is derived from a combination of the Greek word khalkόs ( χαλκός) principally meaning copper (the term was also used for bronze/ brass, any metal in the poetic sense, ore or coin), and the Latinized Greek word genēs, meaning born or produced. Often, oxygen is treated separately from the other chalcogens, sometimes even excluded from the scope of the term "chalcogen" altogether, due to its very different chemical behavior from sulfur, selenium, tellurium, and polonium. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioactive elements polonium (Po) and livermorium (Lv). This group is also known as the oxygen family. Semimetals exhibit properties intermediate between those of metals and nonmetals.The chalcogens (ore forming) ( / ˈ k æ l k ə dʒ ə n z/ KAL-kə-jənz) are the chemical elements in group 16 of the periodic table. The elements can be broadly divided into metals, nonmetals, and semimetals. ![]() Some of the groups have widely-used common names, including the alkali metals (Group 1) and the alkaline earth metals (Group 2) on the far left, and the halogens (Group 17) and the noble gases (Group 18) on the far right. Elements that exhibit similar chemistry appear in vertical columns called groups (numbered 1–18 from left to right) the seven horizontal rows are called periods. It arranges of the elements in order of increasing atomic number. The periodic table is used as a predictive tool. As expected, semimetals exhibit properties intermediate between metals and nonmetals. Most solid nonmetals are brittle, so they break into small pieces when hit with a hammer or pulled into a wire. Nonmetals can be gases (such as chlorine), liquids (such as bromine), or solids (such as iodine) at room temperature and pressure. Nonmetals, in contrast, are generally poor conductors of heat and electricity and are not lustrous. Of the metals, only mercury is a liquid at room temperature and pressure all the rest are solids. The vast majority of the known elements are metals. Metals-such as copper or gold-are good conductors of electricity and heat they can be pulled into wires because they are ductile they can be hammered or pressed into thin sheets or foils because they are malleable and most have a shiny appearance, so they are lustrous. The distinction between metals and nonmetals is one of the most fundamental in chemistry. Gold-colored lements that lie along the diagonal line exhibit properties intermediate between metals and nonmetals they are called semimetals. ![]() \) divides the elements into metals (in blue, below and to the left of the line) and nonmetals (in bronze, above and to the right of the line).
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