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Section: Applications > Food, medicine and cosmetics. Properties of phycobiliproteins, such as their natural antioxidant, anti-inflammatory, food colourant, strong pigment and anti-aging activities, have given them considerable potential for use in food, cosmetics and medicinal applications. They have also proven to be... | Wikipedia - Biliprotein - Applications > Food, medicine and cosmetics | 298 | 1,273 | null |
Section: Applications > Indicator of drinking water quality. The fluorescence signals emitted from phycoerythrin and phycocyanin have made them suitable for use as indicators to detect cyanotoxins such as microcystins in drinking water. A study examined the nature of the biliproteins' fluorescence signals regarding the... | Wikipedia - Biliprotein - Applications > Indicator of drinking water quality | 312 | 1,386 | null |
Article: Bioconcentration. In aquatic toxicology, bioconcentration is the accumulation of a water-borne chemical substance in an organism exposed to the water. There are several ways in which to measure and assess bioaccumulation and bioconcentration. These include: octanol-water partition coefficients (KOW), bioconcen... | Wikipedia - Bioconcentration - Summary | 311 | 1,489 | null |
Section: Calculation. Bioconcentration can be described by a bioconcentration factor (BCF), which is the ratio of the chemical concentration in an organism or biota to the concentration in water: B C F = C o n c e n t r a t i o n B i o t a C o n c e n t r a t i o n W a t e r {\displaystyle BCF={\frac {Concentration_{Bi... | Wikipedia - Bioconcentration - Calculation | 335 | 1,024 | null |
Section: Applications > Equilibrium partitioning models. Based on an assumed steady state scenario, the fate of a chemical in a system is modeled giving predicted endpoint phases and concentrations. It needs to be considered that reaching steady state may need a substantial amount of time as estimated using the followi... | Wikipedia - Bioconcentration - Applications > Equilibrium partitioning models | 152 | 604 | null |
Section: Applications to toxicology > Predictions. Bioconcentration factors facilitate predicting contamination levels in an organism based on chemical concentration in surrounding water. BCF in this setting only applies to aquatic organisms. Air breathing organisms do not take up chemicals in the same manner as other ... | Wikipedia - Bioconcentration - Applications to toxicology > Predictions | 166 | 866 | null |
Section: Biological factors. In determining the degree at which bioconcentration occurs biological factors have to be kept in mind. The rate at which an organism is exposed through respiratory surfaces and contact with dermal surfaces of the organism, competes against the rate of excretion from an organism. The rate of... | Wikipedia - Bioconcentration - Biological factors | 346 | 1,264 | null |
Section: Techniques. Biophysical chemists employ various techniques used in physical chemistry to probe the structure of biological systems. These techniques include spectroscopic methods such as nuclear magnetic resonance (NMR) and other techniques like X-ray diffraction and cryo-electron microscopy. An example of res... | Wikipedia - Biophysical chemistry - Techniques | 254 | 1,302 | null |
Article: Bittern (salt). Bittern (pl. bitterns), or nigari, is the salt solution formed when halite (table salt) precipitates from seawater or brines. Bitterns contain magnesium, calcium, and potassium ions as well as chloride, sulfate, iodide, and other ions. Bittern is commonly formed in salt ponds where the evaporat... | Wikipedia - Bittern (salt) - Summary | 174 | 728 | null |
Section: Uses > Salt derivation. Bittern is a source of many salts including magnesium sulfate (epsom salt). Multiple methods exist for removing these salts from the bittern, and the method ultimately used depends on the target product. Products that would naturally precipitate from the bitterns crystallize as evaporat... | Wikipedia - Bittern (salt) - Uses > Salt derivation | 260 | 1,220 | null |
Section: Uses > Coagulation > Wastewater treatment. Bittern can be used instead of aluminum-based coagulants in the treatment of wastewater produced during the fabric-dyeing process. The wastewater pH is basic, which is favorable for the use of bittern. After the addition of bittern, precipitated magnesium hydroxide wo... | Wikipedia - Bittern (salt) - Uses > Coagulation > Wastewater treatment | 237 | 1,151 | null |
Section: Uses > Other uses. Bittern can be used to culture Haloquadratum archaea. Haloquadratum are distinctly square-shaped and are abundant in hypersaline environments such as salt ponds. Their cultivation is necessary for understanding both their ecological function in those environments as well as their unique morp... | Wikipedia - Bittern (salt) - Uses > Other uses | 228 | 1,111 | null |
Section: Environmental impact. In some jurisdictions, most bitterns are used for other production instead of being directly discarded. In other jurisdictions each tonne of salt produced can create 3+ tonnes of waste bitterns. Although bittern generally contains the same compounds as seawater, it is much more concentrat... | Wikipedia - Bittern (salt) - Environmental impact | 327 | 1,476 | null |
The lack of adequate disposal methods for bitterns and concerns of local commercial and recreational fishing associations about bitterns’ deleterious impacts upon local fish and prawn hatchery areas led the Western Australian EPA in 2008 to recommend against the proposed 4.2 million tonne per annum Straits Salt project... | Wikipedia - Bittern (salt) - Environmental impact | 193 | 985 | null |
Section: Building blocks for medicinal chemistry > Chemical reagents as building blocks. Organic functionalized molecules (reagents), carefully selected for the use in modular synthesis of novel drug candidates, in particular, by combinatorial chemistry, or in order to realize the ideas of virtual screening and drug de... | Wikipedia - Building block (chemistry) - Building blocks for medicinal chemistry > Chemical reagents as building blocks | 165 | 945 | null |
Section: Industrial processes. Carbon monoxide and methanol are important chemical feedstocks. CO is utilized by myriad carbonylation reactions. Together with hydrogen, it is the feed for the Fischer–Tropsch process, which affords liquid fuels. Methanol is the precursor to acetic acid, dimethyl ether, formaldehyde, and... | Wikipedia - C1 chemistry - Industrial processes | 234 | 1,044 | null |
Article: Calconcarboxylic acid. Calconcarboxylic acid (IUPAC name 3-hydroxy-4-[(2-hydroxy-4-sulfonaphthalen-1-yl)diazenyl]naphthalene-2-carboxylic acid; commonly called Patton and Reeder's Indicator) is an azo dye that is used as an indicator for complexometric titrations of calcium with ethylenediaminetetraacetic acid... | Wikipedia - Calconcarboxylic acid - Summary | 154 | 513 | null |
Section: Applications. Calconcarboxylic acid is used for the determination of calcium ion concentration by complexometric titration. Free calconcarboxylic acid is blue colour, but changes to pink/red when it forms a complex with calcium ions. EDTA forms a more stable complex with calcium than calconcarboxylic acid does... | Wikipedia - Calconcarboxylic acid - Applications | 293 | 1,206 | null |
The reaction can be given by: Ca-PR + EDTA4- → PR + [Ca-EDTA]2- The Patton-Reeder Indicator is often used here in the form of a triturate. This method of complexometric titration is dependent on the pH of the solution being sufficiently high to ensure that magnesium ions precipitate as magnesium hydroxide before the PR... | Wikipedia - Calconcarboxylic acid - Applications | 161 | 735 | null |
Section: Carryover effect in clinical laboratory. Carryover experiments are widely used for clinical chemistry and immunochemistry analyzers to evaluate and validate carryover effects. The pipetting and washing systems in an automated analyzer are designed to continuously cycle between the aspiration of patient specime... | Wikipedia - Carryover effect - Carryover effect in clinical laboratory | 168 | 906 | null |
Section: Carryover assessment. IUPAC made a recommendation in 1991 for the description and measurement of carryover effects in clinical chemistry. The carryover ratio is the percentage of H3 carry to L1 constituting the carryover portion "h". In a design of 3 high samples followed by 3 low samples, h can be calculated ... | Wikipedia - Carryover effect - Carryover assessment | 156 | 669 | null |
Article: The central science. Chemistry is often called the central science because of its role in connecting the physical sciences, which include chemistry, with the life sciences, pharmaceutical sciences and applied sciences such as medicine and engineering. The nature of this relationship is one of the main topics i... | Wikipedia - The central science - Summary | 347 | 1,828 | null |
In the same way, biology cannot be fully reduced to chemistry, although the machinery that is responsible for life is composed of molecules. For instance, the machinery of evolution may be described in terms of chemistry by the understanding that it is a mutation in the order of genetic base pairs in the DNA of an orga... | Wikipedia - The central science - Summary | 191 | 1,115 | null |
Article: Charged aerosol detector. The charged aerosol detector (CAD) is a detector used in conjunction with high-performance liquid chromatography (HPLC) and ultra high-performance liquid chromatography (UHPLC) to measure the amount of chemicals in a sample by creating charged aerosol particles which are detected usin... | Wikipedia - Charged aerosol detector - Summary | 211 | 929 | null |
Section: History. The predecessor to the CAD, termed an evaporative electrical detector, was first described by Kaufman in 2002 at TSI Inc in US patent 6,568,245 and was based on the coupling of liquid chromatographic approaches to TSI's electrical aerosol measurement (EAM) technology. At around the same time Dixon and... | Wikipedia - Charged aerosol detector - History | 230 | 1,088 | null |
Section: Principles of operation. The general detection scheme involves: Pneumatic nebulization of mobile phase from the analytical column forming an aerosol. Aerosol conditioning to remove large droplets. Evaporation of solvent from the droplets to form dried particles. Particle charging using an ion jet formed via co... | Wikipedia - Charged aerosol detector - Principles of operation | 154 | 808 | null |
Section: Performance and comparison to other aerosol detectors. The CAD and evaporative light scattering detector (ELSD) are mass-flow sensitive detectors (response is proportional to mass of analyte reaching the detector per unit time) as opposed to concentration sensitive (response is proportional to analyte concentr... | Wikipedia - Charged aerosol detector - Performance and comparison to other aerosol detectors | 265 | 1,286 | null |
Article: Chemical bath deposition. Chemical bath deposition, also called chemical solution deposition and CBD, is a method of thin-film deposition (solids forming from a solution or gas), using an aqueous precursor solution. Chemical bath deposition typically forms films using heterogeneous nucleation (deposition or ad... | Wikipedia - Chemical bath deposition - Summary | 198 | 951 | null |
Section: Uses > Historical Uses. Chemical bath deposition has a long history but until recently was an uncommon method of thin-film deposition. In 1865, Justus Liebig published an article describing the use of chemical bath deposition to silver mirrors (to affix a reflective layer of silver to the back of glass to form... | Wikipedia - Chemical bath deposition - Uses > Historical Uses | 175 | 871 | null |
Section: Uses > Photovoltaics. Photovoltaic cells are the most common use of films deposited by chemical bath deposition because many films have better photovoltaic properties when deposited via CBD than when deposited by other methods. This is because thin films formed by chemical bath deposition exhibit greater size ... | Wikipedia - Chemical bath deposition - Uses > Photovoltaics | 158 | 794 | null |
Section: Uses > Nanomaterials. Chemical bath deposition or electroless deposition has great applications in the field of nanomaterials, because the small crystal size enables formation on the nanometer scale, because the properties and nanostructure of chemical bath deposition films can be precisely controlled, and bec... | Wikipedia - Chemical bath deposition - Uses > Nanomaterials | 150 | 763 | null |
Section: Process. Chemical bath deposition relies on creating a solution such that deposition (changing from an aqueous to a solid substance) will only occur on the substrate, using the method below: Metal salts and (usually) chalcogenide precursors are added to water to form an aqueous solution containing the metal io... | Wikipedia - Chemical bath deposition - Process | 336 | 1,614 | null |
Section: Process > Ion-by-ion mechanism. In ion-by-ion deposition, aqueous precursor ions react directly to form the thin film. The conditions are controlled such that few hydroxide ions form to prevent deposition (not on the substrate) or precipitation of insoluble metal hydroxide. Sometimes a complexing agent is used... | Wikipedia - Chemical bath deposition - Process > Ion-by-ion mechanism | 195 | 872 | null |
Section: Process > Hydroxide-cluster mechanism. Hydroxide-cluster deposition occurs when hydroxide ions are present in the solution and usually results in smaller and more uniform crystals than ion-by-ion deposition. When hydroxide ions are present in the solution in quantity, metal hydroxide ions form. The hydroxide i... | Wikipedia - Chemical bath deposition - Process > Hydroxide-cluster mechanism | 291 | 1,251 | null |
Section: Process > Substrate. Unlike other methods of thin-film deposition, most any substrate which is chemically stable in the aqueous solution can theoretically be used in chemical bath deposition. The desired properties of the film usually dictate the choice of substrate; for example, when light transparency is des... | Wikipedia - Chemical bath deposition - Process > Substrate | 155 | 709 | null |
Section: History. Although considered a relatively new scientific field, the term "chemical biology" has been in use since the early 20th century, and has roots in scientific discovery from the early 19th century. The term 'chemical biology' can be traced back to an early appearance in a book published by Alonzo E. Tay... | Wikipedia - Chemical biology - History | 329 | 1,636 | null |
Section: Research areas > Peptide synthesis. Chemical synthesis of proteins is a valuable tool in chemical biology as it allows for the introduction of non-natural amino acids as well as residue-specific incorporation of "posttranslational modifications" such as phosphorylation, glycosylation, acetylation, and even ubi... | Wikipedia - Chemical biology - Research areas > Peptide synthesis | 274 | 1,407 | null |
Section: Research areas > Enrichment techniques for proteomics. Chemical biologists work to improve proteomics through the development of enrichment strategies, chemical affinity tags, and new probes. Samples for proteomics often contain many peptide sequences and the sequence of interest may be highly represented or o... | Wikipedia - Chemical biology - Research areas > Enrichment techniques for proteomics | 154 | 821 | null |
Section: Research areas > Enzyme probes. To investigate enzymatic activity as opposed to total protein, activity-based reagents have been developed to label the enzymatically active form of proteins (see Activity-based proteomics). For example, serine hydrolase- and cysteine protease-inhibitors have been converted to s... | Wikipedia - Chemical biology - Research areas > Enzyme probes | 163 | 868 | null |
Section: Research areas > Directed evolution. A primary goal of protein engineering is the design of novel peptides or proteins with a desired structure and chemical activity. Because our knowledge of the relationship between primary sequence, structure, and function of proteins is limited, rational design of new prote... | Wikipedia - Chemical biology - Research areas > Directed evolution | 252 | 1,395 | null |
Section: Research areas > Bioorthogonal reactions. Successful labeling of a molecule of interest requires specific functionalization of that molecule to react chemospecifically with an optical probe. For a labeling experiment to be considered robust, that functionalization must minimally perturb the system. Unfortunate... | Wikipedia - Chemical biology - Research areas > Bioorthogonal reactions | 349 | 1,632 | null |
Section: Research areas > Discovery of biomolecules through metagenomics. The advances in modern sequencing technologies in the late 1990s allowed scientists to investigate DNA of communities of organisms in their natural environments ("eDNA"), without culturing individual species in the lab. This metagenomic approach ... | Wikipedia - Chemical biology - Research areas > Discovery of biomolecules through metagenomics | 346 | 1,842 | null |
Substrate-induced gene expression screening (SIGEX), a method to screen for the expression of genes that are induced by chemical compounds, has also been used to search for genes with specific functions. Homology-based metagenomic studies have led to a fast discovery of genes that have homologous sequences as the previ... | Wikipedia - Chemical biology - Research areas > Discovery of biomolecules through metagenomics | 193 | 953 | null |
Section: Research areas > Kinases. Posttranslational modification of proteins with phosphate groups by kinases is a key regulatory step throughout all biological systems. Phosphorylation events, either phosphorylation by protein kinases or dephosphorylation by phosphatases, result in protein activation or deactivation.... | Wikipedia - Chemical biology - Research areas > Kinases | 344 | 1,731 | null |
For example, a "bisubstrate analog" inhibits kinase action by binding both the conserved ATP binding pocket and a protein/peptide recognition site on the specific kinase. Research groups also utilized ATP analogs as chemical probes to study kinases and identify their substrates. The development of novel chemical means ... | Wikipedia - Chemical biology - Research areas > Kinases | 339 | 1,640 | null |
For example, the development of peptide biosensors—peptides containing incorporated fluorophores improved temporal resolution of in vitro binding assays. One of the most useful techniques to study kinase action is Fluorescence Resonance Energy Transfer (FRET). To utilize FRET for phosphorylation studies, fluorescent pr... | Wikipedia - Chemical biology - Research areas > Kinases | 166 | 787 | null |
Section: Research areas > Biological fluorescence. Chemical biologists often study the functions of biological macromolecules using fluorescence techniques. The advantage of fluorescence versus other techniques resides in its high sensitivity, non-invasiveness, safe detection, and ability to modulate the fluorescence s... | Wikipedia - Chemical biology - Research areas > Biological fluorescence | 326 | 1,573 | null |
Both fluorescent proteins and biarsenical tetracysteine can be expressed in live cells, but present major limitations in ectopic expression and might cause a loss of function. Fluorescent techniques have been used to assess a number of protein dynamics including protein tracking, conformational changes, protein–protein... | Wikipedia - Chemical biology - Research areas > Biological fluorescence | 345 | 1,761 | null |
Article: Chemical compound. A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element is therefore not a compound. A compound can be tra... | Wikipedia - Chemical compound - Summary | 232 | 1,299 | null |
Section: History of the concept > Robert Boyle. The term "compound"—with a meaning similar to the modern—has been used at least since 1661 when Robert Boyle's The Sceptical Chymist was published. In this book, Boyle variously used the terms "compound", "compounded body", "perfectly mixt body", and "concrete". "Perfectl... | Wikipedia - Chemical compound - History of the concept > Robert Boyle | 177 | 749 | null |
Section: History of the concept > Isaac Watts. In his Logick, published in 1724, the English minister and logician Isaac Watts gave an early definition of chemical element, and contrasted element with chemical compound in clear, modern terms. Among Substances, some are called Simple, some are Compound ... Simple Substa... | Wikipedia - Chemical compound - History of the concept > Isaac Watts | 282 | 1,300 | null |
Section: Definitions. Any substance consisting of two or more different types of atoms (chemical elements) in a fixed stoichiometric proportion can be termed a chemical compound; the concept is most readily understood when considering pure chemical substances.: 15 It follows from their being composed of fixed proportio... | Wikipedia - Chemical compound - Definitions | 339 | 1,731 | null |
Pure chemical elements are generally not considered chemical compounds, failing the two or more atom requirement, though they often consist of molecules composed of multiple atoms (such as in the diatomic molecule H2, or the polyatomic molecule S8, etc.). Many chemical compounds have a unique numerical identifier assig... | Wikipedia - Chemical compound - Definitions | 296 | 1,558 | null |
Section: Types > Ionic compounds. An ionic compound is a chemical compound composed of ions held together by electrostatic forces termed ionic bonding. The compound is neutral overall, but consists of positively charged ions called cations and negatively charged ions called anions. These can be simple ions such as the ... | Wikipedia - Chemical compound - Types > Ionic compounds | 275 | 1,381 | null |
Section: Bonding and forces. Compounds are held together through a variety of different types of bonding and forces. The differences in the types of bonds in compounds differ based on the types of elements present in the compound. London dispersion forces are the weakest force of all intermolecular forces. They are tem... | Wikipedia - Chemical compound - Bonding and forces | 321 | 1,676 | null |
Article: Chemical element. A chemical element is a chemical substance whose atoms all have the same number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen atom has 8 protons in its nucleus. Atoms of the same element can have diffe... | Wikipedia - Chemical element - Summary | 311 | 1,589 | null |
The term "(chemical) element" is used in two different but closely related meanings: it can mean a chemical substance consisting of a single kind of atom (a free element), or it can mean that kind of atom as a component of various chemical substances. For example, water (H2O) consists of the elements hydrogen (H) and o... | Wikipedia - Chemical element - Summary | 315 | 1,407 | null |
Nearly all other naturally occurring elements occur in the Earth as compounds or mixtures. Air is mostly a mixture of molecular nitrogen and oxygen, though it does contain compounds including carbon dioxide and water, as well as atomic argon, a noble gas which is chemically inert and therefore does not undergo chemical... | Wikipedia - Chemical element - Summary | 315 | 1,713 | null |
Section: Description. The lightest elements are hydrogen and helium, both created by Big Bang nucleosynthesis in the first 20 minutes of the universe in a ratio of around 3:1 by mass (or 12:1 by number of atoms), along with tiny traces of the next two elements, lithium and beryllium. Almost all other elements found in ... | Wikipedia - Chemical element - Description | 310 | 1,470 | null |
Some of these elements, notably bismuth (atomic number 83), thorium (atomic number 90), and uranium (atomic number 92), have one or more isotopes with half-lives long enough to survive as remnants of the explosive stellar nucleosynthesis that produced the heavy metals before our Solar System formed. At 2×1019 years, ov... | Wikipedia - Chemical element - Description | 318 | 1,409 | null |
These 94 elements have been detected in the universe at large, in the spectra of stars and also supernovae, where short-lived radioactive elements are newly being made. The first 94 elements have been detected directly on Earth as primordial nuclides present from the formation of the Solar System, or as naturally occur... | Wikipedia - Chemical element - Description | 316 | 1,640 | null |
Section: Description > Atomic number. The atomic number of an element is equal to the number of protons in each atom, and defines the element. For example, all carbon atoms contain 6 protons in their atomic nucleus; so the atomic number of carbon is 6. Carbon atoms may have different numbers of neutrons; atoms of the s... | Wikipedia - Chemical element - Description > Atomic number | 229 | 1,151 | null |
Section: Description > Isotopes. Isotopes are atoms of the same element (that is, with the same number of protons in their nucleus), but having different numbers of neutrons. Thus, for example, there are three main isotopes of carbon. All carbon atoms have 6 protons, but they can have either 6, 7, or 8 neutrons. Since ... | Wikipedia - Chemical element - Description > Isotopes | 325 | 1,378 | null |
Section: Description > Isotopic mass and atomic mass. The mass number of an element, A, is the number of nucleons (protons and neutrons) in the atomic nucleus. Different isotopes of a given element are distinguished by their mass number, which is written as a superscript on the left hand side of the chemical symbol (e.... | Wikipedia - Chemical element - Description > Isotopic mass and atomic mass | 330 | 1,411 | null |
For example, the atomic mass of chlorine-35 to five significant digits is 34.969 Da and that of chlorine-37 is 36.966 Da. However, the relative atomic mass of each isotope is quite close to its mass number (always within 1%). The only isotope whose atomic mass is exactly a natural number is 12C, which has a mass of 12 ... | Wikipedia - Chemical element - Description > Isotopic mass and atomic mass | 267 | 1,138 | null |
Section: Description > Chemically pure and isotopically pure. Chemists and nuclear scientists have different definitions of a pure element. In chemistry, a pure element means a substance whose atoms all (or in practice almost all) have the same atomic number, or number of protons. Nuclear scientists, however, define a ... | Wikipedia - Chemical element - Description > Chemically pure and isotopically pure | 176 | 783 | null |
Section: Description > Allotropes. Atoms of chemically pure elements may bond to each other chemically in more than one way, allowing the pure element to exist in multiple chemical structures (spatial arrangements of atoms), known as allotropes, which differ in their properties. For example, carbon can be found as diam... | Wikipedia - Chemical element - Description > Allotropes | 304 | 1,376 | null |
Section: Description > Properties > General properties. Several terms are commonly used to characterise the general physical and chemical properties of the chemical elements. A first distinction is between metals, which readily conduct electricity, nonmetals, which do not, and a small group, (the metalloids), having in... | Wikipedia - Chemical element - Description > Properties > General properties | 283 | 1,359 | null |
Section: Description > Properties > Densities. The density at selected standard temperature and pressure (STP) is often used in characterizing the elements. Density is often expressed in grams per cubic centimetre (g/cm3). Since several elements are gases at commonly encountered temperatures, their densities are usuall... | Wikipedia - Chemical element - Description > Properties > Densities | 189 | 833 | null |
Section: Description > Properties > Occurrence and origin on Earth. Chemical elements may also be categorised by their origin on Earth, with the first 94 considered naturally occurring, while those with atomic numbers beyond 94 have only been produced artificially via human-made nuclear reactions. Of the 94 naturally o... | Wikipedia - Chemical element - Description > Properties > Occurrence and origin on Earth | 321 | 1,541 | null |
Elements with atomic numbers 43, 61, and 83 through 94 are unstable enough that their radioactive decay can be detected. Three of these elements, bismuth (element 83), thorium (90), and uranium (92) have one or more isotopes with half-lives long enough to survive as remnants of the explosive stellar nucleosynthesis tha... | Wikipedia - Chemical element - Description > Properties > Occurrence and origin on Earth | 174 | 786 | null |
Section: Description > Periodic table. The properties of the elements are often summarized using the periodic table, which powerfully and elegantly organizes the elements by increasing atomic number into rows ("periods") in which the columns ("groups") share recurring ("periodic") physical and chemical properties. The ... | Wikipedia - Chemical element - Description > Periodic table | 214 | 1,197 | null |
Section: Nomenclature and symbols > Atomic numbers. The known elements have atomic numbers from 1 to 118, conventionally presented as Arabic numerals. Since the elements can be uniquely sequenced by atomic number, conventionally from lowest to highest (as in a periodic table), sets of elements are sometimes specified b... | Wikipedia - Chemical element - Nomenclature and symbols > Atomic numbers | 172 | 775 | null |
Section: Nomenclature and symbols > Element names. The naming of various substances now known as elements precedes the atomic theory of matter, as names were given locally by various cultures to various minerals, metals, compounds, alloys, mixtures, and other materials, though at the time it was not known which chemica... | Wikipedia - Chemical element - Nomenclature and symbols > Element names | 329 | 1,492 | null |
For purposes of international communication and trade, the official names of the chemical elements both ancient and more recently recognised are decided by the International Union of Pure and Applied Chemistry (IUPAC), which has decided on a sort of international English language, drawing on traditional English names e... | Wikipedia - Chemical element - Nomenclature and symbols > Element names | 348 | 1,538 | null |
These are also named by IUPAC, which generally adopts the name chosen by the discoverer. This practice can lead to the controversial question of which research group actually discovered an element, a question that delayed the naming of elements with atomic number of 104 and higher for a considerable amount of time. (Se... | Wikipedia - Chemical element - Nomenclature and symbols > Element names | 165 | 825 | null |
Section: Nomenclature and symbols > Chemical symbols > Specific elements. Before chemistry became a science, alchemists designed arcane symbols for both metals and common compounds. These were however used as abbreviations in diagrams or procedures; there was no concept of atoms combining to form molecules. With his ad... | Wikipedia - Chemical element - Nomenclature and symbols > Chemical symbols > Specific elements | 281 | 1,383 | null |
However, in eleven cases Latin (as used by Berzelius) and English names of elements have different roots. Eight of them are the seven metals of antiquity and a metalloid also known since antiquity: "Fe" (Latin ferrum) for iron, "Hg" (Latin hydrargyrum) for mercury, "Sn" (Latin stannum) for tin, "Au" (Latin aurum) for g... | Wikipedia - Chemical element - Nomenclature and symbols > Chemical symbols > Specific elements | 313 | 1,203 | null |
The use of Latin as the universal language of science was fading, but chemical names of newly discovered elements came to be borrowed from language to language with little or no modification. Symbols of elements discovered after 1814 match their names in English, French (ignoring the acute accent on ⟨é⟩), and German (t... | Wikipedia - Chemical element - Nomenclature and symbols > Chemical symbols > Specific elements | 254 | 1,100 | null |
Section: Nomenclature and symbols > Chemical symbols > General chemical symbols. There are also symbols in chemical equations for groups of elements, for example in comparative formulas. These are often a single capital letter, and the letters are reserved and not used for names of specific elements. For example, "X" i... | Wikipedia - Chemical element - Nomenclature and symbols > Chemical symbols > General chemical symbols | 286 | 1,227 | null |
Section: Nomenclature and symbols > Chemical symbols > Isotope symbols. Isotopes of an element are distinguished by mass number (total protons and neutrons), with this number combined with the element's symbol. IUPAC prefers that isotope symbols be written in superscript notation when practical, for example 12C and 235... | Wikipedia - Chemical element - Nomenclature and symbols > Chemical symbols > Isotope symbols | 183 | 761 | null |
Section: Origin of the elements. Only about 4% of the total mass of the universe is made of atoms or ions, and thus represented by elements. This fraction is about 15% of the total matter, with the remainder of the matter (85%) being dark matter. The nature of dark matter is unknown, but it is not composed of atoms of ... | Wikipedia - Chemical element - Origin of the elements | 341 | 1,567 | null |
In the early phases of the Big Bang, nucleosynthesis of hydrogen resulted in the production of hydrogen-1 (protium, 1H) and helium-4 (4He), as well as a smaller amount of deuterium (2H) and tiny amounts (on the order of 10−10) of lithium and beryllium. Even smaller amounts of boron may have been produced in the Big Ban... | Wikipedia - Chemical element - Origin of the elements | 292 | 1,226 | null |
These include some produced by cosmic rays or other nuclear reactions (see cosmogenic and nucleogenic nuclides), and others produced as decay products of long-lived primordial nuclides. For example, trace (but detectable) amounts of carbon-14 (14C) are continually produced in the air by cosmic rays impacting nitrogen a... | Wikipedia - Chemical element - Origin of the elements | 242 | 1,147 | null |
Section: Abundance. The following graph (note log scale) shows the abundance of elements in our Solar System. The table shows the 12 most common elements in our galaxy (estimated spectroscopically), as measured in parts per million by mass. Nearby galaxies that have evolved along similar lines have a corresponding enri... | Wikipedia - Chemical element - Abundance | 333 | 1,686 | null |
Iron-56 is particularly common, since it is the most stable nuclide that can easily be made from alpha particles (being a product of decay of radioactive nickel-56, ultimately made from 14 helium nuclei). Elements heavier than iron are made in energy-absorbing processes in large stars, and their abundance in the univer... | Wikipedia - Chemical element - Abundance | 283 | 1,371 | null |
Aluminium at 8% by mass is more common in the Earth's crust than in the universe and solar system, but the composition of the far more bulky mantle, which has magnesium and iron in place of aluminium (which occurs there only at 2% of mass) more closely mirrors the elemental composition of the solar system, save for the... | Wikipedia - Chemical element - Abundance | 210 | 1,009 | null |
Section: History > Classical definitions. Ancient philosophy posited a set of classical elements to explain observed patterns in nature. These elements originally referred to earth, water, air and fire rather than the chemical elements of modern science. The term 'elements' (stoicheia) was first used by Greek philosoph... | Wikipedia - Chemical element - History > Classical definitions | 204 | 955 | null |
Section: History > Chemical definitions > Robert Boyle. In 1661, in The Sceptical Chymist, Robert Boyle proposed his theory of corpuscularism which favoured the analysis of matter as constituted of irreducible units of matter (atoms); and, choosing to side with neither Aristotle's view of the four elements nor Paracels... | Wikipedia - Chemical element - History > Chemical definitions > Robert Boyle | 348 | 1,543 | null |
Propos. I. ... At the first Production of mixt Bodies, the Universal Matter whereof they ... consisted, was actually divided into little Particles. ... The Generation ... and wasting of Bodies ... and ... the Chymical Resolutions of mixt Bodies, and ... Operations of ... Fires upon them ... manifest their consisting of... | Wikipedia - Chemical element - History > Chemical definitions > Robert Boyle | 347 | 1,289 | null |
Quicksilver ... with Aqua fortis will be brought into a ... white Powder ... with Sulphur it will compose a blood-red ... Cinaber. And yet out of all these exotick Compounds, we may recover the very same running Mercury. ... Propos. III. ... From most of such mixt Bodies ... there may by the Help of the Fire, be actual... | Wikipedia - Chemical element - History > Chemical definitions > Robert Boyle | 238 | 942 | null |
Section: History > Chemical definitions > Isaac Watts. In 1724, in his book Logick, the English minister and logician Isaac Watts enumerated the elements then recognised by chemists. Watts' list of elements included two of Paracelsus' principles (sulfur and salt) and two classical elements (earth and water) as well as ... | Wikipedia - Chemical element - History > Chemical definitions > Isaac Watts | 229 | 1,022 | null |
Section: History > Chemical definitions > Antoine Lavoisier, Jöns Jacob Berzelius, and Dmitri Mendeleev. The first modern list of elements was given in Antoine Lavoisier's 1789 Elements of Chemistry, which contained 33 elements, including light and caloric. By 1818, Jöns Jacob Berzelius had determined atomic weights fo... | Wikipedia - Chemical element - History > Chemical definitions > Antoine Lavoisier, Jöns Jacob Berzelius, and Dmitri Mendeleev | 159 | 777 | null |
Section: History > Atomic definitions. The 1913 discovery by English physicist Henry Moseley that the nuclear charge is the physical basis for the atomic number, further refined when the nature of protons and neutrons became appreciated, eventually led to the current definition of an element based on atomic number (num... | Wikipedia - Chemical element - History > Atomic definitions | 248 | 1,239 | null |
Section: History > Discovery and recognition of various elements. Ten materials familiar to various prehistoric cultures are now known to be elements: Carbon, copper, gold, iron, lead, mercury, silver, sulfur, tin, and zinc. Three additional materials now accepted as elements, arsenic, antimony, and bismuth, were recog... | Wikipedia - Chemical element - History > Discovery and recognition of various elements | 252 | 1,182 | null |
Most of the remaining naturally occurring elements were identified and characterised by 1900, including: Such now-familiar industrial materials as aluminium, silicon, nickel, chromium, magnesium, and tungsten Reactive metals such as lithium, sodium, potassium, and calcium The halogens fluorine, chlorine, bromine, and i... | Wikipedia - Chemical element - History > Discovery and recognition of various elements | 268 | 1,205 | null |
Section: History > Recently discovered elements. The first transuranium element (element with an atomic number greater than 92) discovered was neptunium in 1940. Since 1999, the IUPAC/IUPAP Joint Working Party has considered claims for the discovery of new elements. As of January 2016, all 118 elements have been confir... | Wikipedia - Chemical element - History > Recently discovered elements | 211 | 972 | null |
Section: Structure. A chemical equation (see an example below) consists of a list of reactants (the starting substances) on the left-hand side, an arrow symbol, and a list of products (substances formed in the chemical reaction) on the right-hand side. Each substance is specified by its chemical formula, optionally pre... | Wikipedia - Chemical equation - Structure | 264 | 1,198 | null |
Section: Structure > State of matter. To indicate physical state of a chemical, a symbol in parentheses may be appended to its formula: (s) for a solid, (l) for a liquid, (g) for a gas, and (aq) for an aqueous solution. This is especially done when one wishes to emphasize the states or changes thereof. For example, the... | Wikipedia - Chemical equation - Structure > State of matter | 258 | 955 | null |
Section: Structure > Catalysis and other conditions. If the reaction requires energy, it is indicated above the arrow. A capital Greek letter delta (Δ) or a triangle (△) is put on the reaction arrow to show that energy in the form of heat is added to the reaction. The expression hν is used as a symbol for the addition ... | Wikipedia - Chemical equation - Structure > Catalysis and other conditions | 201 | 904 | null |
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