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136-466: Boron is a chemical element . It has the symbol   B and atomic number  5. In its crystalline form it is a brittle, dark, lustrous metalloid ; in its amorphous form it is a brown powder. As the lightest element of the boron group it has three valence electrons for forming covalent bonds , resulting in many compounds such as boric acid , the mineral sodium borate , and the ultra-hard crystals of boron carbide and boron nitride . Boron

272-679: A government monopoly on the mining of borate minerals in Turkey, which possesses 72% of the world's known deposits. In 2012, it held a 47% share of production of global borate minerals, ahead of its main competitor, Rio Tinto Group . Almost a quarter (23%) of global boron production comes from the single Rio Tinto Borax Mine (also known as the U.S. Borax Boron Mine) 35°2′34.447″N 117°40′45.412″W  /  35.04290194°N 117.67928111°W  / 35.04290194; -117.67928111  ( Rio Tinto Borax Mine ) near Boron, California . The average cost of crystalline elemental boron

408-738: 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 pure element as one that consists of only one isotope. For example, a copper wire is 99.99% chemically pure if 99.99% of its atoms are copper, with 29 protons each. However it is not isotopically pure since ordinary copper consists of two stable isotopes, 69% Cu and 31% Cu, with different numbers of neutrons. However, pure gold would be both chemically and isotopically pure, since ordinary gold consists only of one isotope, Au. Atoms of chemically pure elements may bond to each other chemically in more than one way, allowing

544-451: A superacid . As one example, carboranes form useful molecular moieties that add considerable amounts of boron to other biochemicals in order to synthesize boron-containing compounds for boron neutron capture therapy for cancer. As anticipated by its hydride clusters , boron forms a variety of stable compounds with formal oxidation state less than three. B 2 F 4 and B 4 Cl 4 are well characterized. Binary metal-boron compounds,

680-418: A busy, booming centre of mining and smelting works with hundreds of shafts for Agricola to investigate. His primary post proved to be not very demanding and he lent all his spare time to his studies. Beginning in 1528 he immersed himself in comparisons and tests on what had been written about mineralogy and mining and his own observations of the local materials and the methods of their treatment. He constructed

816-421: A celebrated humanist of the time and adherent of Erasmus of Rotterdam . Gifted with a precocious intellect and his freshly acquired title of Baccalaureus artium , Agricola early threw himself into the pursuit of the " new learning ", with such effect that at the age of 24 he was appointed Rector extraordinarius of Ancient Greek at the 1519 established Zwickau Greek school , which was soon to be united with

952-456: A comprehensive textbook and account of the discovery and occurrence of minerals, ores, metals, gemstones, earths and igneous rocks, followed by De animantibus subterraneis in 1548 and a number of smaller works on the metals during the following two years. Agricola served as Burgomaster (lord mayor) of Chemnitz in 1546, 1547, 1551 and 1553. Agricola's most famous work, the De re metallica libri xii

1088-549: A considerable amount of time. (See element naming controversy ). Precursors of such controversies involved the nationalistic namings of elements in the late 19th century. For example, lutetium was named in reference to Paris, France. The Germans were reluctant to relinquish naming rights to the French, often calling it cassiopeium . Similarly, the British discoverer of niobium originally named it columbium , in reference to

1224-477: A different element in nuclear reactions , which change an atom's atomic number. Historically, the term "chemical element" meant a substance that cannot be broken down into constituent substances by chemical reactions, and for most practical purposes this definition still has validity. There was some controversy in the 1920s over whether isotopes deserved to be recognized as separate elements if they could be separated by chemical means. The term "(chemical) element"

1360-652: A few decay products, to have been differentiated from other elements. Most recently, the synthesis of element 118 (since named oganesson ) was reported in October 2006, and the synthesis of element 117 ( tennessine ) was reported in April 2010. Of these 118 elements, 94 occur naturally on Earth. Six of these occur in extreme trace quantities: technetium , atomic number 43; promethium , number 61; astatine , number 85; francium , number 87; neptunium , number 93; and plutonium , number 94. These 94 elements have been detected in

1496-529: A few elements, such as silver and gold , are found uncombined as relatively pure native element minerals . 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 reactions. The history of

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1632-646: A fractional difference between the B and B and traditionally expressed in parts per thousand, in natural waters ranging from −16 to +59. There are 13 known isotopes of boron; the shortest-lived isotope is B which decays through proton emission and alpha decay with a half-life of 3.5×10 s. Isotopic fractionation of boron is controlled by the exchange reactions of the boron species B(OH) 3 and [B(OH) 4 ] . Boron isotopes are also fractionated during mineral crystallization, during H 2 O phase changes in hydrothermal systems, and during hydrothermal alteration of rock . The latter effect results in preferential removal of

1768-556: A future subject of investigation. In 1531 Christian Egenolff in Frankfurt published his German book named Rechter Gebrauch d'Alchimei, mitt vil bissher verborgenen, nutzbaren unnd lustigen Künsten, nit allein den fürwitzigen Alchimismisten, sonder allen kunstbaren Werckleutten, in und ausserhalb Feurs. Auch sunst aller menglichen inn vil wege zugebrauchen ( The Proper Use of Alchemy ) which argued that true "alchemy" should not attempt transmutation of metals to gold or synthesizing

1904-411: A logical system of the local conditions, rocks and sediments, the minerals and ores, explained the various terms of general and specific local territorial features. He combined this discourse on all natural aspects with a treatise on the actual mining, the methods and processes, local extraction variants, the differences and oddities he had learnt from the miners. For the first time, he tackled questions on

2040-539: A new element and named it boracium . Gay-Lussac and Thénard used iron to reduce boric acid at high temperatures. By oxidizing boron with air, they showed that boric acid is its oxidation product. Jöns Jacob Berzelius identified it as an element in 1824. Pure boron was arguably first produced by the American chemist Ezekiel Weintraub in 1909. Some early routes to elemental boron involved the reduction of boric oxide with metals such as magnesium or aluminium . However,

2176-500: A pressure of 1 bar and a given temperature (typically at 298.15K). However, for phosphorus, the reference state is white phosphorus even though it is not the most stable allotrope, and the reference state for carbon is graphite, because the structure of graphite is more stable than that of the other allotropes. In thermochemistry , an element is defined to have an enthalpy of formation of zero in its reference state. Several kinds of descriptive categorizations can be applied broadly to

2312-483: A pressure of one atmosphere, are commonly used in characterizing the various elements. While known for most elements, either or both of these measurements is still undetermined for some of the radioactive elements available in only tiny quantities. Since helium remains a liquid even at absolute zero at atmospheric pressure, it has only a boiling point, and not a melting point, in conventional presentations. The density at selected standard temperature and pressure (STP)

2448-403: A protective oxide or hydroxide layer is formed on the surface of boron, which prevents further corrosion. The rate of oxidation of boron depends on the crystallinity, particle size, purity and temperature. At higher temperatures boron burns to form boron trioxide : Boron undergoes halogenation to give trihalides; for example, The trichloride in practice is usually made from the oxide. Boron

2584-456: A small group, (the metalloids ), having intermediate properties and often behaving as semiconductors . A more refined classification is often shown in colored presentations of the periodic table. This system restricts the terms "metal" and "nonmetal" to only certain of the more broadly defined metals and nonmetals, adding additional terms for certain sets of the more broadly viewed metals and nonmetals. The version of this classification used in

2720-484: A tendency to form novel dodecahedral (12-sided) and icosahedral (20-sided) structures composed completely of boron atoms, or with varying numbers of carbon heteroatoms. Organoboron chemicals have been employed in uses as diverse as boron carbide (see below), a complex very hard ceramic composed of boron-carbon cluster anions and cations, to carboranes , carbon-boron cluster chemistry compounds that can be halogenated to form reactive structures including carborane acid ,

2856-403: A trigonal planar configuration. Unlike silicates, boron minerals never contain it with coordination number greater than four. A typical motif is exemplified by the tetraborate anions of the common mineral borax . The formal negative charge of the tetrahedral borate center is balanced by metal cations in the minerals, such as the sodium (Na) in borax. The tourmaline group of borate-silicates is also

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2992-608: A very important boron-bearing mineral group, and a number of borosilicates are also known to exist naturally. Boranes are chemical compounds of boron and hydrogen, with the generic formula of B x H y . These compounds do not occur in nature. Many of the boranes readily oxidise on contact with air, some violently. The parent member BH 3 is called borane, but it is known only in the gaseous state, and dimerises to form diborane, B 2 H 6 . The larger boranes all consist of boron clusters that are polyhedral, some of which exist as isomers. For example, isomers of B 20 H 26 are based on

3128-474: A whole number. For example, the relative atomic mass of chlorine is 35.453 u, which differs greatly from a whole number as it is an average of about 76% chlorine-35 and 24% chlorine-37. Whenever a relative atomic mass value differs by more than ~1% from a whole number, it is due to this averaging effect, as significant amounts of more than one isotope are naturally present in a sample of that element. Chemists and nuclear scientists have different definitions of

3264-505: A wide range of subjects and disciplines, such as pedagogy , medicine, metrology , mercantilism , pharmacy , philosophy, geology, history, and many more. His innovative and comprehensive scholarly work, based on new and precise methods of production and control, has made his work a central part of scholarship and understanding of science during that period. He is often, although not universally referred to as "the Father of mineralogy " and

3400-404: Is 10 (for tin , element 50). 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.g., U). The mass number is always an integer and has units of "nucleons". Thus, magnesium-24 (24

3536-455: Is US$ 5/g. Elemental boron is chiefly used in making boron fibers, where it is deposited by chemical vapor deposition on a tungsten core (see below). Boron fibers are used in lightweight composite applications, such as high strength tapes. This use is a very small fraction of total boron use. Boron is introduced into semiconductors as boron compounds, by ion implantation. Estimated global consumption of boron (almost entirely as boron compounds)

3672-606: Is a mixture of C (about 98.9%), C (about 1.1%) and about 1 atom per trillion of C. Most (54 of 94) naturally occurring elements have more than one stable isotope. Except for the isotopes of hydrogen (which differ greatly from each other in relative mass—enough to cause chemical effects), the isotopes of a given element are chemically nearly indistinguishable. All elements have radioactive isotopes (radioisotopes); most of these radioisotopes do not occur naturally. Radioisotopes typically decay into other elements via alpha decay , beta decay , or inverse beta decay ; some isotopes of

3808-406: Is a dimensionless number equal to the atomic mass divided by the atomic mass constant , which equals 1 Da. In general, the mass number of a given nuclide differs in value slightly from its relative atomic mass, since the mass of each proton and neutron is not exactly 1 Da; since the electrons contribute a lesser share to the atomic mass as neutron number exceeds proton number; and because of

3944-536: Is a relatively poor electrical and thermal conductor in the planar directions. A large number of organoboron compounds are known and many are useful in organic synthesis . Many are produced from hydroboration , which employs diborane , B 2 H 6 , a simple borane chemical, or carboboration . Organoboron(III) compounds are usually tetrahedral or trigonal planar, for example, tetraphenylborate , [B(C 6 H 5 ) 4 ] vs. triphenylborane , B(C 6 H 5 ) 3 . However, multiple boron atoms reacting with each other have

4080-452: Is a relatively rare element in the Earth's crust, representing only 0.001% of the crust mass, it can be highly concentrated by the action of water, in which many borates are soluble. It is found naturally combined in compounds such as borax and boric acid (sometimes found in volcanic spring waters). About a hundred borate minerals are known. On 5 September 2017, scientists reported that

4216-452: Is an additive in fiberglass for insulation and structural materials. The next leading use is in polymers and ceramics in high-strength, lightweight structural and heat-resistant materials. Borosilicate glass is desired for its greater strength and thermal shock resistance than ordinary soda lime glass. As sodium perborate , it is used as a bleach . A small amount is used as a dopant in semiconductors , and reagent intermediates in

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4352-508: Is an essential plant nutrient . The word boron was coined from borax , the mineral from which it was isolated, by analogy with carbon , which boron resembles chemically. Borax in its mineral form (then known as tincal) first saw use as a glaze, beginning in China circa 300 AD. Some crude borax traveled westward, and was apparently mentioned by the alchemist Jabir ibn Hayyan around 700 AD. Marco Polo brought some glazes back to Italy in

4488-812: Is an ongoing area of scientific study. 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 nature were made by various natural methods of nucleosynthesis . On Earth, small amounts of new atoms are naturally produced in nucleogenic reactions, or in cosmogenic processes, such as cosmic ray spallation . New atoms are also naturally produced on Earth as radiogenic daughter isotopes of ongoing radioactive decay processes such as alpha decay , beta decay , spontaneous fission , cluster decay , and other rarer modes of decay. Of

4624-460: Is based on a Latin or other traditional word, for example adopting "gold" rather than "aurum" as the name for the 79th element (Au). IUPAC prefers the British spellings " aluminium " and "caesium" over the U.S. spellings "aluminum" and "cesium", and the U.S. "sulfur" over British "sulphur". However, elements that are practical to sell in bulk in many countries often still have locally used national names, and countries whose national language does not use

4760-782: Is called the atomic number of that element. For example, oxygen has an atomic number of 8, meaning each oxygen atom has 8 protons in its nucleus. Atoms of the same element can have different numbers of neutrons in their nuclei, known as isotopes of the element. Two or more atoms can combine to form molecules . Some elements are formed from molecules of identical atoms , e. g. atoms of hydrogen (H) form diatomic molecules (H 2 ). Chemical compounds are substances made of atoms of different elements; they can have molecular or non-molecular structure. Mixtures are materials containing different chemical substances; that means (in case of molecular substances) that they contain different types of molecules. Atoms of one element can be transformed into atoms of

4896-548: Is high energy spallation neutrons. Such neutrons can be moderated by materials high in light elements, such as polyethylene , but the moderated neutrons continue to be a radiation hazard unless actively absorbed in the shielding. Among light elements that absorb thermal neutrons, Li and B appear as potential spacecraft structural materials which serve both for mechanical reinforcement and radiation protection. Cosmic radiation will produce secondary neutrons if it hits spacecraft structures. Those neutrons will be captured in B, if it

5032-436: Is often used in characterizing the elements. Density is often expressed in grams per cubic centimetre (g/cm ). Since several elements are gases at commonly encountered temperatures, their densities are usually stated for their gaseous forms; when liquefied or solidified, the gaseous elements have densities similar to those of the other elements. When an element has allotropes with different densities, one representative allotrope

5168-420: Is present in the spacecraft's semiconductors , producing a gamma ray , an alpha particle , and a lithium ion. Those resultant decay products may then irradiate nearby semiconductor "chip" structures, causing data loss (bit flipping, or single event upset ). In radiation-hardened semiconductor designs, one countermeasure is to use depleted boron , which is greatly enriched in B and contains almost no B. This

5304-593: Is rare and poorly studied because the pure material is extremely difficult to prepare. Most studies of "boron" involve samples that contain small amounts of carbon. The chemical behavior of boron resembles that of silicon more than aluminium . Crystalline boron is chemically inert and resistant to attack by boiling hydrofluoric or hydrochloric acid . When finely divided, it is attacked slowly by hot concentrated hydrogen peroxide , hot concentrated nitric acid , hot sulfuric acid or hot mixture of sulfuric and chromic acids . When exposed to air, under normal conditions,

5440-638: Is rare in the Universe and solar system due to trace formation in the Big Bang and in stars. It is formed in minor amounts in cosmic ray spallation nucleosynthesis and may be found uncombined in cosmic dust and meteoroid materials. In the high oxygen environment of Earth, boron is always found fully oxidized to borate. Boron does not appear on Earth in elemental form. Extremely small traces of elemental boron were detected in Lunar regolith. Although boron

5576-428: Is selectively taken up by a malignant tumor and tissues near it. The patient is then treated with a beam of low energy neutrons at a relatively low neutron radiation dose. The neutrons, however, trigger energetic and short-range secondary alpha particle and lithium-7 heavy ion radiation that are products of the boron-neutron nuclear reaction , and this ion radiation additionally bombards the tumor, especially from inside

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5712-460: Is silvery to black, extremely hard (9.3 on the Mohs scale ), and a poor electrical conductor at room temperature (1.5 × 10 Ω cm room temperature electrical conductivity). The primary use of the element itself is as boron filaments with applications similar to carbon fibers in some high-strength materials. Boron is primarily used in chemical compounds. About half of all production consumed globally

5848-609: Is synthesized entirely by cosmic ray spallation and supernovas and not by stellar nucleosynthesis , so it is a low-abundance element in the Solar System and in the Earth's crust . It constitutes about 0.001 percent by weight of Earth's crust. It is concentrated on Earth by the water-solubility of its more common naturally occurring compounds, the borate minerals . These are mined industrially as evaporites , such as borax and kernite . The largest known deposits are in Turkey ,

5984-506: Is the lightest element having an electron in a p-orbital in its ground state. Unlike most other p-elements , it rarely obeys the octet rule and usually places only six electrons (in three molecular orbitals ) onto its valence shell . Boron is the prototype for the boron group (the IUPAC group  13), although the other members of this group are metals and more typical p-elements (only aluminium to some extent shares boron's aversion to

6120-426: Is the mass number) is an atom with 24 nucleons (12 protons and 12 neutrons). Whereas the mass number simply counts the total number of neutrons and protons and is thus an integer, the atomic mass of a particular isotope (or "nuclide") of the element is the mass of a single atom of that isotope, and is typically expressed in daltons (symbol: Da), or universal atomic mass units (symbol: u). Its relative atomic mass

6256-439: Is the most common and stable. An α-tetragonal phase also exists (α-T), but is very difficult to produce without significant contamination. Most of the phases are based on B 12 icosahedra, but the γ phase can be described as a rocksalt -type arrangement of the icosahedra and B 2 atomic pairs. It can be produced by compressing other boron phases to 12–20 GPa and heating to 1500–1800 °C; it remains stable after releasing

6392-532: Is typically selected in summary presentations, while densities for each allotrope can be stated where more detail is provided. For example, the three familiar allotropes of carbon ( amorphous carbon , graphite , and diamond ) have densities of 1.8–2.1, 2.267, and 3.515 g/cm , respectively. The elements studied to date as solid samples have eight kinds of crystal structures : cubic , body-centered cubic , face-centered cubic, hexagonal , monoclinic , orthorhombic , rhombohedral , and tetragonal . For some of

6528-552: Is used as an abrasive, as it has a hardness comparable with diamond (the two substances are able to produce scratches on each other). In the BN compound analogue of graphite, hexagonal boron nitride (h-BN), the positively charged boron and negatively charged nitrogen atoms in each plane lie adjacent to the oppositely charged atom in the next plane. Consequently, graphite and h-BN have very different properties, although both are lubricants, as these planes slip past each other easily. However, h-BN

6664-438: Is used in the petrochemical industry as a catalyst. The halides react with water to form boric acid . It is found in nature on Earth almost entirely as various oxides of B(III), often associated with other elements. More than one hundred borate minerals contain boron in oxidation state +3. These minerals resemble silicates in some respect, although it is often found not only in a tetrahedral coordination with oxygen, but also in

6800-417: Is used in two different but closely related meanings: it can mean a chemical substance consisting of a single kind of atoms, or it can mean that kind of atoms as a component of various chemical substances. For example, molecules of water (H 2 O) contain atoms of hydrogen (H) and oxygen (O), so water can be said as a compound consisting of the elements hydrogen (H) and oxygen (O) even though it does not contain

6936-430: Is used up and the fuel becomes less reactive. In future crewed interplanetary spacecraft, B has a theoretical role as structural material (as boron fibers or BN nanotube material) which would also serve a special role in the radiation shield. One of the difficulties in dealing with cosmic rays , which are mostly high energy protons, is that some secondary radiation from interaction of cosmic rays and spacecraft materials

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7072-632: Is useful because B is largely immune to radiation damage. Depleted boron is a byproduct of the nuclear industry (see above). B is also a candidate as a fuel for aneutronic fusion . When struck by a proton with energy of about 500 k eV , it produces three alpha particles and 8.7 MeV of energy. Most other fusion reactions involving hydrogen and helium produce penetrating neutron radiation, which weakens reactor structures and induces long-term radioactivity, thereby endangering operating personnel. The alpha particles from B fusion can be turned directly into electric power, and all radiation stops as soon as

7208-446: Is useful for capturing thermal neutrons (see neutron cross section#Typical cross sections ). The nuclear industry enriches natural boron to nearly pure B. The less-valuable by-product, depleted boron, is nearly pure B. Because of its high neutron cross-section, boron-10 is often used to control fission in nuclear reactors as a neutron-capturing substance. Several industrial-scale enrichment processes have been developed; however, only

7344-429: Is very strong; fullerenes , which have nearly spherical shapes; and carbon nanotubes , which are tubes with a hexagonal structure (even these may differ from each other in electrical properties). The ability of an element to exist in one of many structural forms is known as 'allotropy'. The reference state of an element is defined by convention, usually as the thermodynamically most stable allotrope and physical state at

7480-482: Is well known for his pioneering work De re metallica libri XII , that was published in 1556, one year after his death. This 12-volume work is a comprehensive and systematic study, classification and methodical guide on all available factual and practical aspects, that are of concern for mining , the mining sciences and metallurgy , investigated and researched in its natural environment by means of direct observation. Unrivalled in its complexity and accuracy, it served as

7616-590: Is widely used. For example, the French chemical terminology distinguishes élément chimique (kind of atoms) and corps simple (chemical substance consisting of a single kind of atoms); the Russian chemical terminology distinguishes химический элемент and простое вещество . Almost all baryonic matter in the universe is composed of elements (among rare exceptions are neutron stars ). When different elements undergo chemical reactions, atoms are rearranged into new compounds held together by chemical bonds . Only

7752-680: The Curiosity rover detected boron, an essential ingredient for life on Earth , on the planet Mars . Such a finding, along with previous discoveries that water may have been present on ancient Mars, further supports the possible early habitability of Gale Crater on Mars. Economically important sources of boron are the minerals colemanite , rasorite ( kernite ), ulexite and tincal . Together these constitute 90% of mined boron-containing ore. The largest global borax deposits known, many still untapped, are in Central and Western Turkey , including

7888-476: The Great School of Zwickau (Zwickauer Ratsschule). In 1520 he published his first book, a Latin grammar manual with practical and methodical hints for teachers. In 1522 he ended his appointment to again study at Leipzig for another year, where, as rector, he was supported by his former tutor and professor of classics, Peter Mosellanus , with whom he had always been in correspondence. He also subscribed to

8024-489: The International Union of Pure and Applied Chemistry (IUPAC) had recognized a total of 118 elements. The first 94 occur naturally on Earth , and the remaining 24 are synthetic elements produced in nuclear reactions. Save for unstable radioactive elements (radioelements) which decay quickly, nearly all elements are available industrially in varying amounts. The discovery and synthesis of further new elements

8160-638: The Latin alphabet are likely to use the IUPAC element names. According to IUPAC, element names are not proper nouns; therefore, the full name of an element is not capitalized in English, even if derived from a proper noun , as in californium and einsteinium . Isotope names are also uncapitalized if written out, e.g., carbon-12 or uranium-235 . Chemical element symbols (such as Cf for californium and Es for einsteinium), are always capitalized (see below). In

8296-514: The Leipzig professor Petrus Mosellanus convinced him to consider the common practice of name latinisation , particularly popular among Renaissance scholars, so "Georg Pawer" became "Georgius Agricola". Coincidentally, the name Georg/Georgius derives from Greek and also means "farmer". Agricola was born in 1494 as Georg Pawer, the second of seven children of a clothier and dyer in Glauchau. At

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8432-592: The New World . It was used extensively as such by American publications before the international standardization (in 1950). 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 advances in the atomic theory of matter, John Dalton devised his own simpler symbols, based on circles, to depict molecules. Georgius Agricola He

8568-423: The kinetic isotope effect is significant). Thus, all carbon isotopes have nearly identical chemical properties because they all have six electrons, even though they may have 6 to 8 neutrons. That is why atomic number, rather than mass number or atomic weight , is considered the identifying characteristic of an element. The symbol for atomic number is Z . Isotopes are atoms of the same element (that is, with

8704-405: The nuclear binding energy and electron binding energy. 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 C, which has a mass of 12 Da; because

8840-501: The philosopher's stone but rather study and develop the industrial methods of skilled craftsmen. In the same year Agricola received an offer of the city of Kepmnicz (Chemnitz) for the position of Stadtleybarzt ( town physician ), which he accepted and he relocated to Chemnitz in 1533. Although little is known about his work as physician, Agricola entered his most productive years and soon became lord mayor of Chemnitz and served as diplomat and historiographer for Duke George , who

8976-590: The synthesis of organic fine chemicals . A few boron-containing organic pharmaceuticals are used or are in study. Natural boron is composed of two stable isotopes, one of which ( boron-10 ) has a number of uses as a neutron-capturing agent. The intersection of boron with biology is very small. Consensus on it as essential for mammalian life is lacking. Borates have low toxicity in mammals (similar to table salt ) but are more toxic to arthropods and are occasionally used as insecticides . Boron-containing organic antibiotics are known. Although only traces are required, it

9112-555: The 13th century. Georgius Agricola , in around 1600, reported the use of borax as a flux in metallurgy . In 1777, boric acid was recognized in the hot springs ( soffioni ) near Florence , Italy, at which point it became known as sal sedativum , with ostensible medical benefits. The mineral was named sassolite , after Sasso Pisano in Italy. Sasso was the main source of European borax from 1827 to 1872, when American sources replaced it. Boron compounds were relatively rarely used until

9248-502: The 16th century Holy Roman Empire there were no uniform dimensions, measures, and weights, which impeded trade and commerce. This work laid the foundation for Agricola's reputation as a humanist scholar; as he committed himself to the introduction of standardized weights and measures, he entered the public stage and occupied a political position. In 1544, he published the De ortu et causis subterraneorum (On Subterranean Origins and Causes), in which he criticized older theories and laid out

9384-638: The 94 naturally occurring elements, those with atomic numbers 1 through 82 each have at least one stable isotope (except for technetium , element 43 and promethium , element 61, which have no stable isotopes). Isotopes considered stable are those for which no radioactive decay has yet been observed. Elements with atomic numbers 83 through 94 are unstable to the point that radioactive decay of all isotopes can be detected. 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

9520-470: The Elder 's work Historia Naturalis was the main source of information on metals and mining techniques. Agricola acknowledged his debt to ancient authors, such as Pliny and Theophrastus , and made numerous references to Roman works. In geology , Agricola described and illustrated how ore veins occur in and on the ground. He described prospecting for ore veins and surveying in detail, as well as washing

9656-487: The French, Italians, Greeks, Portuguese and Poles prefer "azote/azot/azoto" (from roots meaning "no life") for "nitrogen". For purposes of international communication and trade, the official names of the chemical elements both ancient and more recently recognized 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 even when an element's chemical symbol

9792-644: The United States . Agricola died on November 21, 1555. His "lifelong friend," the Protestant poet and classicist Georg Fabricius , wrote in a letter to the Protestant theologian Phillip Melanchthon , "He who since the days of childhood had enjoyed robust health was carried off by a four-days' fever." Agricola was a fervent Catholic, who, according to Fabricius, "despised our Churches" and "would not tolerate with patience that anyone should discuss ecclesiastical matters with him". That did not stop Fabricius in

9928-458: The [B(OH) 4 ] ion onto clays. It results in solutions enriched in B(OH) 3 and therefore may be responsible for the large B enrichment in seawater relative to both oceanic crust and continental crust; this difference may act as an isotopic signature . The exotic B exhibits a nuclear halo , i.e. its radius is appreciably larger than that predicted by the liquid drop model . The B isotope

10064-595: The age of twelve he enrolled in the Latin school in Chemnitz or Zwickau . From 1514 to 1518 he studied at the Leipzig University where, under the name Georgius Pawer de Glauchaw , he first subscribed in the summer semester to theology, philosophy and philology under rector Nikolaus Apel and to ancient languages, Greek and Latin in particular. He received his first Latin lectures under Petrus Mosellanus ,

10200-487: The atomic masses of the elements (their atomic weights or atomic masses) do not always increase monotonically with their atomic numbers. 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 chemicals were elements and which compounds. As they were identified as elements,

10336-526: The black rock of the Schloßberg at Stolpen to be the same as Pliny the Elder's basalt , Agricola applied this name to it, and thus originated a petrological term. In 1912, the Mining Magazine (London) published an English translation of De re metallica . The translation was made by Herbert Hoover , the American mining engineer and his wife Lou Henry Hoover . Hoover was later President of

10472-476: The borons is then simply the ratio of hydrogen to boron in the molecule. For example, in diborane B 2 H 6 , the boron oxidation state is +3, but in decaborane B 10 H 14 , it is / 5 or +1.4. In these compounds the oxidation state of boron is often not a whole number. The boron nitrides are notable for the variety of structures that they adopt. They exhibit structures analogous to various allotropes of carbon , including graphite, diamond, and nanotubes. In

10608-413: The chemical substances (di)hydrogen (H 2 ) and (di)oxygen (O 2 ), as H 2 O molecules are different from H 2 and O 2 molecules. For the meaning "chemical substance consisting of a single kind of atoms", the terms "elementary substance" and "simple substance" have been suggested, but they have not gained much acceptance in English chemical literature, whereas in some other languages their equivalent

10744-402: The cluster compounds dodecaborate ( B 12 H 12 ), decaborane (B 10 H 14 ), and the carboranes such as C 2 B 10 H 12 . Characteristically such compounds contain boron with coordination numbers greater than four. Boron has two naturally occurring and stable isotopes , B (80.1%) and B (19.9%). The mass difference results in a wide range of δB values, which are defined as

10880-480: The contemplated high luminosity version of the Large Hadron Collider . Certain other metal borides find specialized applications as hard materials for cutting tools. Often the boron in borides has fractional oxidation states, such as −1/3 in calcium hexaboride (CaB 6 ). From the structural perspective, the most distinctive chemical compounds of boron are the hydrides. Included in this series are

11016-408: The dalton is defined as 1/12 of the mass of a free neutral carbon-12 atom in the ground state. The standard atomic weight (commonly called "atomic weight") of an element is the average of the atomic masses of all the chemical element's isotopes as found in a particular environment, weighted by isotopic abundance, relative to the atomic mass unit. This number may be a fraction that is not close to

11152-466: The diamond-like structure, called cubic boron nitride (tradename Borazon ), boron atoms exist in the tetrahedral structure of carbon atoms in diamond, but one in every four B-N bonds can be viewed as a coordinate covalent bond , wherein two electrons are donated by the nitrogen atom which acts as the Lewis base to a bond to the Lewis acidic boron(III) centre. Cubic boron nitride, among other applications,

11288-416: The discovery and use of elements began with early human societies that discovered native minerals like carbon , sulfur , copper and gold (though the modern concept of an element was not yet understood). Attempts to classify materials such as these resulted in the concepts of classical elements , alchemy , and similar theories throughout history. Much of the modern understanding of elements developed from

11424-406: The elements are available by name, atomic number, density, melting point, boiling point and chemical symbol , as well as ionization energy . The nuclides of stable and radioactive elements are also available as a list of nuclides , sorted by length of half-life for those that are unstable. One of the most convenient, and certainly the most traditional presentation of the elements, is in the form of

11560-470: 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 table contains 118 confirmed elements as of 2021. Although earlier precursors to this presentation exist, its invention is generally credited to Russian chemist Dmitri Mendeleev in 1869, who intended

11696-480: 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 by such notation as "through", "beyond", or "from ... through", as in "through iron", "beyond uranium", or "from lanthanum through lutetium". The terms "light" and "heavy" are sometimes also used informally to indicate relative atomic numbers (not densities), as in "lighter than carbon" or "heavier than lead", though

11832-413: The elements without any stable isotopes are technetium (atomic number 43), promethium (atomic number 61), and all observed elements with atomic number greater than 82. Of the 80 elements with at least one stable isotope, 26 have only one stable isotope. The mean number of stable isotopes for the 80 stable elements is 3.1 stable isotopes per element. The largest number of stable isotopes for a single element

11968-474: The elements, including consideration of their general physical and chemical properties, their states of matter under familiar conditions, their melting and boiling points, their densities, their crystal structures as solids, and their origins. Several terms are commonly used to characterize 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

12104-492: The existing names for anciently known elements (e.g., gold, mercury, iron) were kept in most countries. National differences emerged over the element names either for convenience, linguistic niceties, or nationalism. For example, German speakers use "Wasserstoff" (water substance) for "hydrogen", "Sauerstoff" (acid substance) for "oxygen" and "Stickstoff" (smothering substance) for "nitrogen"; English and some other languages use "sodium" for "natrium", and "potassium" for "kalium"; and

12240-630: The explosive stellar nucleosynthesis that produced the heavy metals before the formation of our Solar System . At over 1.9 × 10 years, over a billion times longer than the estimated age of the universe, bismuth-209 has the longest known alpha decay half-life of any isotope, and is almost always considered on par with the 80 stable elements. The heaviest elements (those beyond plutonium, element 94) undergo radioactive decay with half-lives so short that they are not found in nature and must be synthesized . There are now 118 known elements. In this context, "known" means observed well enough, even from just

12376-529: The formation of Earth, they are certain to have completely decayed, and if present in novae, are in quantities too small to have been noted. Technetium was the first purportedly non-naturally occurring element synthesized, in 1937, though trace amounts of technetium have since been found in nature (and also the element may have been discovered naturally in 1925). This pattern of artificial production and later natural discovery has been repeated with several other radioactive naturally occurring rare elements. List of

12512-632: The formation of elemental boron, but exploits the convenient availability of borates. Boron is similar to carbon in its capability to form stable covalently bonded molecular networks. Even nominally disordered ( amorphous ) boron contains regular boron icosahedra which are bonded randomly to each other without long-range order . Crystalline boron is a very hard, black material with a melting point of above 2000 °C. It forms four major allotropes : α-rhombohedral and β-rhombohedral (α-R and β-R), γ-orthorhombic (γ) and β-tetragonal (β-T). All four phases are stable at ambient conditions , and β-rhombohedral

12648-619: The formation of ores and minerals, attempted to bring the underlying mechanisms to light and introduce his conclusions in a systematic framework. He laid out the whole process in a scholarly dialogue and published it under the title Bermannus, sive de re metallica dialogus , (Bermannus, or a dialogue on metallurgy) in 1530. The work was highly praised by Erasmus for the attempt to put the knowledge, won by practical inquiry into order and further investigate in reduced form. Agricola, in his capacity of physician, also suggested, that minerals and their effects on and relationship to human medicine should be

12784-531: The foundations of modern physical geology . It discusses the effect of wind and water as powerful geological forces, the origin and distribution of ground water and mineralizing fluids, the origin of subterranean heat, the origin of ore channels, and the principal divisions of the mineral kingdom. However, he maintained that a certain 'materia pinguis' or 'fatty matter,' set into fermentation by heat, gave birth to fossil organic shapes, as opposed to fossil shells having belonged to living animals. In 1546, he published

12920-527: The founder of geology as a scientific discipline. Poet Georg Fabricius has bestowed a brief honorary title on him in recognition of his legacy, that his fellow Saxons cite regularly: die ausgezeichnete Zierde des Vaterlandes , (literally: the distinguished ornament of the Fatherland ). He was baptized with his birth name Georg Pawer . Pawer is a vernacular form of the modern German term Bauer , which translates to farmer in English. His teacher,

13056-435: The four volumes of De natura eorum quae effluunt e terra (The nature of the things that flow out of the earth's interior). It deals with the properties of water, its effects, taste, smell, temperature etc. and air under the earth, which, as Agricola reasoned, is responsible for earthquakes and volcanoes. The ten books of De veteribus et novis metallis , more commonly known as De Natura Fossilium were published in 1546 as

13192-412: The fractionated vacuum distillation of the dimethyl ether adduct of boron trifluoride (DME-BF 3 ) and column chromatography of borates are being used. Enriched boron or B is used in both radiation shielding and is the primary nuclide used in neutron capture therapy of cancer . In the latter ("boron neutron capture therapy" or BNCT), a compound containing B is incorporated into a pharmaceutical which

13328-488: The friendship in a network among the many scholars, including the most celebrated, from all over Europe, whom he had encouraged to come to Venice and take care of the redaction of the numerous publications of the classics of antiquity . At the time of Agricola's visit, the business was run by Andrea Torresani and his daughter Maria. Agricola participated in the edition of a work in several volumes on Galen until 1526. He returned to Zwickau in 1527 and to Chemnitz in autumn of

13464-433: The fusion of two 10-atom clusters. The most important boranes are diborane B 2 H 6 and two of its pyrolysis products, pentaborane B 5 H 9 and decaborane B 10 H 14 . A large number of anionic boron hydrides are known, e.g. [B 12 H 12 ]. The formal oxidation number in boranes is positive, and is based on the assumption that hydrogen is counted as −1 as in active metal hydrides. The mean oxidation number for

13600-431: The half-lives predicted for the observationally stable lead isotopes range from 10 to 10 years. 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 that produced

13736-399: The heaviest elements also undergo spontaneous fission . Isotopes that are not radioactive, are termed "stable" isotopes. All known stable isotopes occur naturally (see primordial nuclide ). The many radioisotopes that are not found in nature have been characterized after being artificially produced. Certain elements have no stable isotopes and are composed only of radioisotopes: specifically

13872-549: The heavy elements before the formation of the Solar System. For example, at over 1.9 × 10 years, over a billion times longer than the estimated age of the universe, bismuth-209 has the longest known alpha decay half-life of any isotope. The last 24 elements (those beyond plutonium, element 94) undergo radioactive decay with short half-lives and cannot be produced as daughters of longer-lived elements, and thus are not known to occur in nature at all. 1 The properties of

14008-418: The largest producer of boron minerals. Elemental boron is a metalloid that is found in small amounts in meteoroids , but chemically uncombined boron is not otherwise found naturally on Earth. Industrially, the very pure element is produced with difficulty because of contamination by carbon or other elements that resist removal. Several allotropes exist: amorphous boron is a brown powder; crystalline boron

14144-549: The late 1800s when Francis Marion Smith 's Pacific Coast Borax Company first popularized and produced them in volume at low cost. Boron was not recognized as an element until it was isolated by Sir Humphry Davy and by Joseph Louis Gay-Lussac and Louis Jacques Thénard . In 1808 Davy observed that electric current sent through a solution of borates produced a brown precipitate on one of the electrodes. In his subsequent experiments, he used potassium to reduce boric acid instead of electrolysis . He produced enough boron to confirm

14280-508: The local mother church. His religious affiliation, however, outweighed his secular prerogatives and monumental services for the city. Chemnitz Protestant superintendent Tettelbach urged Prince August to command the refusal of a burial inside the city. The command was issued and Tettelbach immediately informed the Agricola party. Upon the initiative of his childhood friend, Naumburg bishop Julius von Pflug , four days later Agricola's body

14416-412: The metal borides, contain boron in negative oxidation states. Illustrative is magnesium diboride (MgB 2 ). Each boron atom has a formal −1 charge and magnesium is assigned a formal charge of +2. In this material, the boron centers are trigonal planar with an extra double bond for each boron, forming sheets akin to the carbon in graphite . However, unlike hexagonal boron nitride, which lacks electrons in

14552-450: The most familiar compounds, boron has the formal oxidation state III. These include oxides, borates, sulfides, nitrides, and halides. The trihalides adopt a planar trigonal structure. These compounds are Lewis acids in that they readily form adducts with electron-pair donors, which are called Lewis bases . For example, fluoride (F) and boron trifluoride (BF 3 ) combined to give the tetrafluoroborate anion, BF 4 . Boron trifluoride

14688-428: The octet rule). Boron also has much lower electronegativity than subsequent period 2 elements . For the latter, lithium salts are common e.g. lithium fluoride , lithium hydroxide , lithium amide , and methyllithium , but lithium boryllides are extraordinarily rare. Strong bases do not deprotonate a borohydride R 2 BH to the boryl anion R 2 B, instead forming the octet-complete adduct R 2 HB-base. In

14824-576: The ores to collect the heavier valuable minerals, such as gold and tin . The work shows water mills used in mining , such as the machine for lifting men and material into and out of a mine shaft . Water mills found application especially in crushing ores to release the fine particles of gold and other heavy minerals, as well as working giant bellows to force air into the confined spaces of underground workings. Agricola described mining methods which are now obsolete, such as fire-setting , which involved building fires against hard rock faces. The hot rock

14960-418: The periodic table, which groups together elements with similar chemical properties (and usually also similar electronic structures). 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

15096-426: The periodic tables presented here includes: actinides , alkali metals , alkaline earth metals , halogens , lanthanides , transition metals , post-transition metals , metalloids , reactive nonmetals , and noble gases . In this system, the alkali metals, alkaline earth metals, and transition metals, as well as the lanthanides and the actinides, are special groups of the metals viewed in a broader sense. Similarly,

15232-451: The plane of the covalent atoms, the delocalized electrons in magnesium diboride allow it to conduct electricity similar to isoelectronic graphite. In 2001, this material was found to be a high-temperature superconductor . It is a superconductor under active development. A project at CERN to make MgB 2 cables has resulted in superconducting test cables able to carry 20,000 amperes for extremely high current distribution applications, such as

15368-417: The product was often contaminated with borides of those metals. Pure boron can be prepared by reducing volatile boron halides with hydrogen at high temperatures. Ultrapure boron for use in the semiconductor industry is produced by the decomposition of diborane at high temperatures and then further purified by the zone melting or Czochralski processes . The production of boron compounds does not involve

15504-486: The provinces of Eskişehir , Kütahya and Balıkesir . Global proven boron mineral mining reserves exceed one billion metric tonnes, against a yearly production of about four million tonnes. Turkey and the United States are the largest producers of boron products. Turkey produces about half of the global yearly demand, through Eti Mine Works ( Turkish : Eti Maden İşletmeleri ) a Turkish state-owned mining and chemicals company focusing on boron products. It holds

15640-412: 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 diamond , which has a tetrahedral structure around each carbon atom; graphite , which has layers of carbon atoms with a hexagonal structure stacked on top of each other; graphene , which is a single layer of graphite that

15776-772: The reactive nonmetals and the noble gases are nonmetals viewed in the broader sense. In some presentations, the halogens are not distinguished, with astatine identified as a metalloid and the others identified as nonmetals. Another commonly used basic distinction among the elements is their state of matter (phase), whether solid , liquid , or gas , at standard temperature and pressure (STP). Most elements are solids at STP, while several are gases. Only bromine and mercury are liquid at 0 degrees Celsius (32 degrees Fahrenheit) and 1 atmosphere pressure; caesium and gallium are solid at that temperature, but melt at 28.4°C (83.2°F) and 29.8°C (85.6°F), respectively. Melting and boiling points , typically expressed in degrees Celsius at

15912-407: The reactor is turned off. Both B and B possess nuclear spin . The nuclear spin of B is 3 and that of B is ⁠ 3 / 2 ⁠ . These isotopes are, therefore, of use in nuclear magnetic resonance spectroscopy; and spectrometers specially adapted to detecting the boron-11 nuclei are available commercially. The B and B nuclei also cause splitting in the resonances of attached nuclei. Boron

16048-919: The remaining 11 elements have half lives too short for them to have been present at the beginning of the Solar System, and are therefore considered transient elements. Of these 11 transient elements, five ( polonium , radon , radium , actinium , and protactinium ) are relatively common decay products of thorium and uranium . The remaining six transient elements (technetium, promethium, astatine, francium , neptunium , and plutonium ) occur only rarely, as products of rare decay modes or nuclear reaction processes involving uranium or other heavy elements. Elements with atomic numbers 1 through 82, except 43 (technetium) and 61 (promethium), each have at least one isotope for which no radioactive decay has been observed. Observationally stable isotopes of some elements (such as tungsten and lead ), however, are predicted to be slightly radioactive with very long half-lives: for example,

16184-495: The same element having different numbers of neutrons are known as isotopes of the element. The number of protons in the nucleus also determines its electric charge , which in turn determines the number of electrons of the atom in its non-ionized state. The electrons are placed into atomic orbitals that determine the atom's chemical properties . The number of neutrons in a nucleus usually has very little effect on an element's chemical properties; except for hydrogen (for which

16320-409: The same letter from calling Agricola "that distinguished ornament of our Fatherland," whose "religious views...were compatible with reason, it is true, and were dazzling," though not "compatible with truth"; in 1551 Fabricius had already written the introductory poem to De re metallica in praise of Agricola. According to traditional urban customs, as a former lord mayor he was entitled to a burial in

16456-404: 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 the mass numbers of these are 12, 13 and 14 respectively, said three isotopes are known as carbon-12 , carbon-13 , and carbon-14 ( C, C, and C). Natural carbon

16592-563: The same year, where he married Anna Meyner, a widow from Schneeberg. Upon his search for employment as town physician and pharmacist in the Ore Mountains , preferably a place, where he could satisfy his ardent longings for the studies on mining, he settled in the suitable little town Joachimsthal in the Bohemian Erzgebirge , where in 1516 significant silver ore deposits were found. The 15,000 inhabitants made Joachimsthal

16728-457: The second half of the 20th century, physics laboratories became able to produce elements with half-lives too short for an appreciable amount of them to exist at any time. 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

16864-552: The standard reference work for two centuries. Agricola stated in the preface, that he will exclude "all those things which I have not myself seen, or have not read or heard of". He continued, "That which I have neither seen, nor carefully considered after reading or hearing of, I have not written about." As a scholar of the Renaissance he was committed to a universal approach towards learning and research. He published over 40 complete scholarly works during his professional life on

17000-610: The studies of medicine , physics , and chemistry . In 1523 he traveled to Italy and enrolled in the University of Bologna and probably Padua and completed his studies in medicine. It remains unclear where he acquired his diploma. In 1524 he joined the Aldine Press , a prestigious printing office in Venice that was established by Aldus Manutius , who had died in 1515. Manutius had established and maintained contacts and

17136-496: The synthetically produced transuranic elements, available samples have been too small to determine crystal structures. Chemical elements may also be categorized 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 occurring elements, 83 are considered primordial and either stable or weakly radioactive. The longest-lived isotopes of

17272-955: The table to illustrate recurring trends in the properties of the elements. The layout of the table has been refined and extended over time as new elements have been discovered and new theoretical models have been developed to explain chemical behavior. Use of the periodic table is now ubiquitous in chemistry, providing an extremely useful framework to classify, systematize and compare all the many different forms of chemical behavior. The table has also found wide application in physics , geology , biology , materials science , engineering , agriculture , medicine , nutrition , environmental health , and astronomy . Its principles are especially important in chemical engineering . The various chemical elements are formally identified by their unique atomic numbers, their accepted names, and their chemical symbols . The known elements have atomic numbers from 1 to 118, conventionally presented as Arabic numerals . Since

17408-532: The temperature and pressure. The β-T phase is produced at similar pressures, but higher temperatures of 1800–2200 °C. The α-T and β-T phases might coexist at ambient conditions, with the β-T phase being the more stable. Compressing boron above 160 GPa produces a boron phase with an as yet unknown structure, and this phase is a superconductor at temperatures below 6–12 K. Borospherene ( fullerene -like B 40 molecules) and borophene (proposed graphene -like structure) were described in 2014. Elemental boron

17544-440: The tumor cells. In nuclear reactors, B is used for reactivity control and in emergency shutdown systems . It can serve either function in the form of borosilicate control rods or as boric acid . In pressurized water reactors , B boric acid is added to the reactor coolant after the plant is shut down for refueling. When the plant is started up again, the boric acid is slowly filtered out over many months as fissile material

17680-561: 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 occurring fission or transmutation products of uranium and thorium. The remaining 24 heavier elements, not found today either on Earth or in astronomical spectra, have been produced artificially: all are radioactive, with short half-lives; if any of these elements were present at

17816-528: The work of Dmitri Mendeleev , a Russian chemist who published the first recognizable periodic table in 1869. This table organizes the elements by increasing atomic number into rows (" periods ") in which the columns (" groups ") share recurring ("periodic") physical and chemical properties . The periodic table summarizes various properties of the elements, allowing chemists to derive relationships between them and to make predictions about elements not yet discovered, and potential new compounds. By November 2016,

17952-407: Was about 4 million tonnes of B 2 O 3 in 2012. As compounds such as borax and kernite its cost was US$ 377/tonne in 2019. Boron mining and refining capacities are considered to be adequate to meet expected levels of growth through the next decade. Chemical element A chemical element is a chemical substance whose atoms all have the same number of protons . The number of protons

18088-672: Was carried off to Zeitz , more than 50 km (31 mi) away and interred by von Pflug in the Zeitz cathedral. His wife had a memorial plate commissioned and placed inside, that was already removed during the 17th century. Its text, however has been preserved in the Zeitz annals, and reads: To the physician and mayor of Chemnitz, Georgius Agricola, a man most distinguished by piety and scholarship, who had rendered outstanding services to his city, whose legacy will bestow immortal glory on his name, whose spirit Christ himself absorbed into his eternal kingdom. His mourning wife and children. He died in

18224-506: Was looking to uncover possible territorial claims and commissioned Agricola with a large historical work, the Dominatores Saxonici a prima origine ad hanc aetatem (Lords of Saxony from the beginning to the present time), which took 20 years to accomplish and was only published in 1555 at Freiberg . In his work De Mensuris et ponderibus , published in 1533, he described the systems of Greek and Roman measures and weights. In

18360-405: Was published the year after his death, in 1556; it was perhaps finished in 1550, since the dedication to the elector and his brother is dated to that year. The delay is thought to be due to the book's many woodcuts. The work is a systematic, illustrated treatise on mining and extractive metallurgy . It shows processes to extract ores from the ground, and metals from ore. Until that time, Pliny

18496-479: Was quenched with water, and the thermal shock weakened it enough for easy removal. It was a dangerous method when used underground, and was made redundant by explosives . The work contains, in an appendix, the German equivalents for the technical terms used in the Latin text. Modern words that derive from the work include fluorspar (from which was later named fluorine ) and bismuth . In another example, believing

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