Portal:Chemistry
The Chemistry Portal
Welcome to the chemistry portal. Chemistry is a branch of science. Modern chemistry focuses on the study of elements of the world and the bonds between elements. Chemistry also deals with composition, structure, and properties of substances and the transformations that they undergo. In the study of matter, chemistry also investigates its interactions with energy and itself. Because of the diversity of matter, which is mostly in the form of compounds, chemists often study how atoms of different chemical elements interact to form molecules, and how molecules interact with each other.
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Technetium is a chemical element that has the symbol Tc and the atomic number 43. Pronounced tek-nee-s(h)ee-um, the chemical properties of this silvery grey, radioactive, crystalline transition metal are intermediate between rhenium and manganese. Its short-lived isotope Tc-99m is used in nuclear medicine for a wide variety of diagnostic tests. Tc-99 is used as a gamma ray-free source of beta particles, and its pertechnetate ion (TcO4-) could find use as an anodic corrosion preventer for steel (this possible use is hindered by technetium's radioactivity). The pertechnetate forms a technetium dioxide layer on the steel surface, this TcO2 formation explains how iron powder can be used to remove technetium from water. It is also possible to absorb technetium on activated carbon.
Dmitri Mendeleev predicted many of the properties of element 43, which he called ekamanganese, well before its actual discovery (see Mendeleev's predicted elements). In 1937 its isotope Tc-97 became the first element to be artificially produced, hence its name (from the Greek τεχνητος, meaning "artificial"). Most technetium produced on Earth is a by-product of fission of uranium-235 in nuclear reactors and is extracted from nuclear fuel rods. No isotope of technetium has a half-life longer than 4.2 million years (Tc-98), so its detection in red giants in 1952 helped bolster the theory that stars can produce heavier elements. On earth, technetium occurs naturally only in uranium ores as a product of spontaneous fission; the quantities are minute but have been measured. Selected pictureVitrification is a process of converting a material into a glass-like amorphous solid which is free of any crystalline structure, either by the quick removal or addition of heat, or by mixing with an additive. Vitrification is a proven technique in the disposal and long-term storage of nuclear waste or other hazardous wastes. Waste is mixed with glass-forming chemicals to form molten glass that then solidifies, immobilizing the waste. The final waste form resembles obsidian and is a non-leaching, durable material that effectively traps the waste inside. The above image demonstrates this process. Categories
History and Philosophy of ChemistryMany chemists have an interest in the history of chemistry. Those with philosophical interests will be interested that the philosophy of chemistry has quite recently developed along a path somewhat different from the general philosophy of science. Other articles that might interest you are: There is a Wikipedia Project on the History of Science and a portal for the philosophy of science. Chemistry ResourcesWikipedia:WikiProject Chemicals/Data is a collection of links and references that are useful for chemistry-related works. This includes free online chemical databases, publications, patents, computer programs, and various tools. Science is Fun University of Wisconsin–Madison Chemistry Professor Bassam Z. Shakhashiri, shares the fun of science. megaConverter The Web's best place to figure out what equals what. General Chemistry Online Clear text and comprehensive coverage of general chemistry topics by Fred Senese, Dept. of Chemistry Frostburg State University General Chemistry Demonstration at Purdue Video clips (and descriptions) of lecture demonstrations. Intota Chemistry Experts A large online listing of real-world chemistry expert biographies provides examples of the many areas of expertise and careers in chemistry. Chemistry Webercises Directory A large listing of chemistry resources maintained by Steven Murov, Emeritus Chemistry Professor Modesto Junior College. MathMol MathMol (Mathematics and Molecules) is a good starting point for those interested in the field of molecular modeling. Chemistry Educational Resources and Essential References from Wiley, the world's largest chemistry publisher ABC-Chemistry A directory of free full-text journals in chemistry, biochemistry and related subjects. The Element Song A goofy little song about all of the elements. In the news
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Svante Arrhenius (1859-1927) was a Swedish chemist, and one of the founders of the science of physical chemistry. The Arrhenius equation and the lunar crater Arrhenius are named after him. Arrhenius was the first to explain the fact that neither pure salts nor pure water are conductors, but solutions of salts in water are, due to the dissociation of salt into ions. As an extension of this idea, he proposed that acids were substances which produce hydrogen ions in solution, and that bases were substances which produce hydroxide ions in solution. Arrhenius also developed a theory to explain the ice ages, and first formulated the idea that changes in the levels of carbon dioxide in the atmosphere could substantially alter the surface temperature through the greenhouse effect. He received the Nobel Prize in Chemistry in 1903.
Techniques used by chemistsEquipment used by chemistsChemistry in societyChemistry in industryCompanies: AstraZeneca - Bayer - BP - BASF - Bristol Myers Squibb - Degussa - Dow - DuPont - ExxonMobil - GlaxoSmithKline - The Linde Group - Mitsubishi - Monsanto - Nestlé - OSI - Shell - Sigma-Aldrich - Total WikiProjectsPeriodic Table
This common arrangement of the periodic table separates the lanthanides (lanthanoids) and actinides (actinoids) (the f-block) from other elements. The wide periodic table incorporates the f-block. The extended periodic table adds the 8th and 9th periods, incorporating the f-block and adding the theoretical g-block.
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