Atomic Weight: 78.96. The chemical behavior and reactions of these elements are similar. This is approximately the sum of the number of protons and neutrons in the nucleus. It can convert AC electricity to DC electricity. Interactive periodic table showing names, electrons, and oxidation states. Density (g cm−3) The total electrical charge of the nucleus is therefore +Ze, where e … A short film about the chemistry of Selenium, presented by The Periodic Table of Videos. Element 34 of Periodic table is Selenium with atomic number 34, atomic weight 78.96. Members of a group typically have similar properties and electron configurations in their outer shell. Look up chemical element names, symbols, atomic masses and other properties, visualize trends, or even test your elements knowledge by playing a periodic table game! Half of the distance between two unbonded atoms of the same element when the electrostatic forces are balanced. An integrated supply risk index from 1 (very low risk) to 10 (very high risk). Properties: Selenium has an atomic radius of 117 pm, a melting point of 220.5°C, boiling point of 685°C, with oxidation states of 6, 4, and -2. Hello, this week flaky scalps, skunks, dead polo ponies and an element that makes you stink of garlic. Interactive periodic table with up-to-date element property data collected from authoritative sources. Group Relative atomic mass: 78.971 (8) Selenium was discovered by Jöns Jacob Berzelius (SE) in 1817. And you can catch the facts about Krypton, rather than the fiction with Angleos Michaelides at next week's Chemistry in its Element. For more information on the Visual Elements image see the Uses and properties section below. Density is the mass of a substance that would fill 1 cm3 at room temperature. Allotropes The higher the value, the larger risk there is to supply. It can also convert AC electricity to DC electricity, so is extensively used in rectifiers. A semi-metal that can exist in two forms: as a silvery metal or as a red powder. He became intrigued by ore from a mine near Zalatna which had a metallic sheen and which he suspected was native antimony or bismuth. Boiling point Selenium, symbol Se, has a Simple Monoclinic structure and Gray color. The tendency of an atom to attract electrons towards itself, expressed on a relative scale. Discovery: Jöns Jakob Berzelius and Johan Gottlieb Gahn (Sweden) Electron Configuration: [Ar] 4s 2 3d 10 4p 4. A higher recycling rate may reduce risk to supply. These muds are either roasted with sodium carbonate or sulfuric acid, or smelted with sodium carbonate to release the selenium. It was discovered by Jons J. Berzelius in 1817. The energy released when an electron is added to the neutral atom and a negative ion is formed. Welcome to "A Visual Interpretation of The Table of Elements", the most striking version of the periodic table on the web. Selenium was discovered by Jöns Jacob Berzelius at Stockholm in 1817. We hope that you enjoy your visit to this Site. Yum! Also intriguing to me was a recent study indicating that selenium deficient soils may play a role in susceptibility to HIV/AIDS in Africa. In excess it is carcinogenic and teratogenic (disturbs the development of an embryo or foetus). Most important, so called gray selenium consists of long chains of atoms forming extended helical structures. But it's not all bad news. It is often found in combination with metals like mercury, copper, silver or lead. Selenium is used as a toner for photographing purpose. Where more than one isotope exists, the value given is the abundance weighted average. The transition of a substance directly from the solid to the gas phase without passing through a liquid phase. At first he thought it was the element tellurium because it gave off a strong smell of radishes when heated, but he eventually realised that it was in fact a new element. Electron affinityThe energy released when an electron is added to the neutral atom and a negative ion is formed. Uncombined elements have an oxidation state of 0. red selenium has here sub-forms, alpha, beta and gamma. He also became affected by it personally – it can be absorbed through the skin – and it caused him to experience the bad breath associated with those who work with this element. Each entry has a full citation identifying its source. Krypton is a fictional planet in the DC Comics universe, and the native world of the super-heroes Superman, Supergirl, and Krypto the "super dog". Word Origin: Greek Selene: moon. Group. Our Periodic Element comparison tool allows you to compare Periodic Elements properties side by side for all 118 elements | SchoolMyKids Interactive Dynamic Periodic Table, Periodic Table Element Comparison tool, Element Property trends It is combined with the physical properties of elements like tellurium and sulfur. Selenium exists in only trace amounts around us. Period. Glossary. So it can clear up an itchy scalp but it might make you stink in the process. Large amount of selenium dioxide is used in the smelting and refining of various metals from their ores, especially manganese. The sum of the oxidation states within a compound or ion must equal the overall charge. The Chemical Abstracts Service registry number is a unique identifier of a particular chemical, designed to prevent confusion arising from different languages and naming systems. There have been numerous studies, none of them very conclusive, about the possible role of selenium in cancer prevention, and in increasing the efficacy of chemotherapy. A vertical column in the periodic table. There are various allotropic forms of selenium, that interconvert into each other with varying temperature. The oxidation state of an atom is a measure of the degree of oxidation of an atom. It is found in several forms, but is usually prepared with a crystalline structure. Periodic Table of Elements Selenium was discovered by Swedish chemists J�ns Jacob Berzelius and Johan Gottlieb Gahn in 1817 after analyzing an red precipitate that was contaminating the sulfuric acid (H2SO4) being produced at a chemistry plant in Sweden. It is defined as being the charge that an atom would have if all bonds were ionic. Members of a group typically have similar properties and electron configurations in their outer shell. Data for this section been provided by the British Geological Survey. Selenium is toxic to the scalp fungus that causes dandruff so it is used in some anti-dandruff shampoos. These values were determined using several different methods. It decreases electrical resistance with increased illumination. A horizontal row in the periodic table. The availability of suitable substitutes for a given commodity. 116. Melting point Martin Klaproth, the discoverer of uranium and zirconium had concluded that a red colored byproduct of sulfuric acid production contained tellurium, an element whose compounds he had been studying. Elements are organised into blocks by the orbital type in which the outer electrons are found. Selenium: Symbol: Se: Atomic Number: 34: Atomic Weight: 78.971: Density: 4.819 g/cm 3: Melting Point: 221 °C: Boiling Point: 685 °C: Thermal properties: Phase: Solid: Melting Point: 221 °C: Boiling Point: … But we require it as part of various enzymes, such as glutathione peroxidase, as well as in the thyroid. You may not further copy, alter, distribute or otherwise use any of the materials from this Site without the advance, written consent of the RSC. The arrangements of electrons above the last (closed shell) noble gas. Total number of protons in the nucleus is called the atomic number of the atom and is given the symbol Z. This is where the artist explains his interpretation of the element and the science behind the picture. Selenium trioxide (SeO 3) Interesting facts: It is similar to sulfur in its form and compounds. Selenium is a chemical element in the periodic table that has the symbol Se and atomic number 34. Some elements exist in several different structural forms, called allotropes. A measure of how difficult it is to deform a material. Selenium can also be used to reduce the transmission of sunlight in architectural glass, giving it a bronze tint. Selenium—from Ancient Greek σελήνη (selḗnē) "Moon" – was discovered in 1817 by Jöns Jacob Berzelius, who noted the similarity of the new element t… Block The temperature at which the solid–liquid phase change occurs. Selenium is one of those all too common elements that is essential to life in small quantities, and very toxic in larger quantities. Political stability of top reserve holder. The transition of a substance directly from the solid to the gas phase without passing through a liquid phase. The temperature at which the liquid–gas phase change occurs. The number of protons in an atom. It is widespread, and accumulated in various foods, such as nuts, tuna, and lobster, so it is rare for humans to have a selenium deficiency. Black selenium is converted to grey selenium when temperature is increased to around 180°C. It provides a measure of how difficult it is to extend a material, with a value given by the ratio of tensile strength to tensile strain. Values are given for typical oxidation number and coordination. But I save the best occurrence of selenium in nature for last. Classified as a nonmetal, Selenium is a solid at room temperature. I'm Chris Smith, thank you for listening and goodbye. Data for this section been provided by the. ... Selenium acts as a catalyst in some microorganisms. Selenium. Visit my page about element collecting for a general description, or see photographs of all the samples from the set in a periodic table layout or with bigger pictures in numerical order. Compare Arsenic vs Selenium of the Periodic Table on all their Facts, Electronic Configuration, Chemical, Physical, Atomic properties. And when subjected to rapid melting, selenium acquires a black glass like allotropic form. Medium = substitution is possible but there may be an economic and/or performance impact, Low = substitution is possible with little or no economic and/or performance impact, If you wish to use the Images in a manner not permitted by these terms and conditions please contact the Publishing Services Department. A measure of how difficult it is to compress a substance. Most of the world’s selenium is obtained from the anode muds produced during the electrolytic refining of copper. The images may not be posted on any website, shared in any disc library, image storage mechanism, network system or similar arrangement. CAS number Selenium is widely used as a semiconductor. In fact a little investigation showed me that it was perfectly safe in small amounts. Selenium has atomic number 34, meaning each atom has 34 protons. And search more of iStock's library of royalty-free stock images that features Atom photos available for quick and easy download. What is Selenium? Relative atomic mass Some selenium compounds decolourise glass, while others give a deep red colour. Period It is possible selenium was first observed in about the year 1300 by the alchemist Arnold of Villanova. Selenium has both a photovoltaic action (converts light to electricity) and a photoconductive action (electrical resistance decreases with increased illumination). You may browse, download or print out one copy of the material displayed on the Site for your personal, non-commercial, non-public use, but you must retain all copyright and other proprietary notices contained on the materials. These blocks are named for the characteristic spectra they produce: sharp (s), principal (p), diffuse (d), and fundamental (f). Selenium is an essential trace element for some species, including humans. 78.971. A horizontal row in the periodic table. It was Berzelius who discovered selenium in 1817, as an impurity in sulphuric acid. Our selenium page has over 260 facts that span 106 different quantities. Isotopes 400 micrograms per day is set as the safe upper intake level in humans. But the diversity of uses of selenium does not stop with shampoo and horse food supplements and photovoltaics. Log in, This site uses cookies to improve your experience. It is used to make photocells. This is approximately the sum of the number of protons and neutrons in the nucleus. Selenium is also used as an additive to make stainless steel. You do not have JavaScript enabled. How slighted is this important element! Oxygen group element, any of the six chemical elements making up Group 16 (VIa) of the periodic classification—namely, oxygen (O), sulfur (S), selenium (Se), tellurium (Te), polonium (Po), and livermorium (Lv). It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system. It was first observed by the Swedish scientist Jons Jacob Berzelius. 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