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132-497: It was designed to detect solar neutrinos and prove theories related to the Sun 's energy creation mechanism. Before this experiment (and the SAGE experiment that ran concurrently), there had been no observation of low energy solar neutrinos. The experiment's main components, the tank and the counters, were located in the underground astrophysical laboratory Laboratori Nazionali del Gran Sasso in

264-427: A 1:1 mixture of HCl and H 2 O, the system separates completely into two separate liquid phases. Hydrochloric acid forms an azeotrope with boiling point 108.58 °C at 20.22 g HCl per 100 g solution; thus hydrochloric acid cannot be concentrated beyond this point by distillation. Unlike hydrogen fluoride, anhydrous liquid hydrogen chloride is difficult to work with as a solvent, because its boiling point

396-400: A beta decay reaction may interact in a distant detector as a muon or tau neutrino, as defined by the flavor of the charged lepton produced in the detector. This oscillation occurs because the three mass state components of the produced flavor travel at slightly different speeds, so that their quantum mechanical wave packets develop relative phase shifts that change how they combine to produce

528-430: A chlorine derivative of perchloric acid (HOClO 3 ), similar to the thermally unstable chlorine derivatives of other oxoacids: examples include chlorine nitrate (ClONO 2 , vigorously reactive and explosive), and chlorine fluorosulfate (ClOSO 2 F, more stable but still moisture-sensitive and highly reactive). Dichlorine hexoxide is a dark-red liquid that freezes to form a solid which turns yellow at −180 °C: it

660-414: A chlorofluorinating agent, adding chlorine and fluorine across a multiple bond or by oxidation: for example, it will attack carbon monoxide to form carbonyl chlorofluoride, COFCl. It will react analogously with hexafluoroacetone , (CF 3 ) 2 CO, with a potassium fluoride catalyst to produce heptafluoroisopropyl hypochlorite, (CF 3 ) 2 CFOCl; with nitriles RCN to produce RCF 2 NCl 2 ; and with

792-408: A consequence. For example, an electron neutrino produced in a beta decay reaction may interact in a distant detector as a muon or tau neutrino. The three mass values are not yet known as of 2024, but laboratory experiments and cosmological observations have determined the differences of their squares, an upper limit on their sum (<  2.14 × 10  kg ), and an upper limit on the mass of

924-747: A dangerously powerful and unstable oxidizer. Near the end of the nineteenth century, E. S. Smith patented a method of sodium hypochlorite production involving electrolysis of brine to produce sodium hydroxide and chlorine gas, which then mixed to form sodium hypochlorite. This is known as the chloralkali process , first introduced on an industrial scale in 1892, and now the source of most elemental chlorine and sodium hydroxide. In 1884 Chemischen Fabrik Griesheim of Germany developed another chloralkali process which entered commercial production in 1888. Elemental chlorine solutions dissolved in chemically basic water (sodium and calcium hypochlorite ) were first used as anti- putrefaction agents and disinfectants in

1056-628: A difference between the neutrino and antineutrino could simply be due to one particle with two possible chiralities. As of 2019 , it is not known whether neutrinos are Majorana or Dirac particles. It is possible to test this property experimentally. For example, if neutrinos are indeed Majorana particles, then lepton-number violating processes such as neutrinoless double-beta decay would be allowed, while they would not if neutrinos are Dirac particles. Several experiments have been and are being conducted to search for this process, e.g. GERDA , EXO , SNO+ , and CUORE . The cosmic neutrino background

1188-445: A fluoride ion donor or acceptor (Lewis base or acid), although it does not dissociate appreciably into ClF 2 and ClF 4 ions. Chlorine pentafluoride (ClF 5 ) is made on a large scale by direct fluorination of chlorine with excess fluorine gas at 350 °C and 250 atm, and on a small scale by reacting metal chlorides with fluorine gas at 100–300 °C. It melts at −103 °C and boils at −13.1 °C. It

1320-499: A gamma ray. The coincidence of both events—positron annihilation and neutron capture—gives a unique signature of an antineutrino interaction. In February 1965, the first neutrino found in nature was identified by a group including Frederick Reines and Friedel Sellschop . The experiment was performed in a specially prepared chamber at a depth of 3 km in the East Rand ("ERPM") gold mine near Boksburg , South Africa. A plaque in

1452-464: A higher oxidation state than bromination with Br 2 when multiple oxidation states are available, such as in MoCl 5 and MoBr 3 . Chlorides can be made by reaction of an element or its oxide, hydroxide, or carbonate with hydrochloric acid, and then dehydrated by mildly high temperatures combined with either low pressure or anhydrous hydrogen chloride gas. These methods work best when the chloride product

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1584-593: A laboratory, but is predicted to happen within stars and supernovae. The process affects the abundance of isotopes seen in the universe . Neutrino-induced disintegration of deuterium nuclei has been observed in the Sudbury Neutrino Observatory, which uses a heavy water detector. There are three known types ( flavors ) of neutrinos: electron neutrino ν e , muon neutrino ν μ , and tau neutrino ν τ , named after their partner leptons in

1716-784: A low-pressure discharge tube. The yellow [Cl 3 ] cation is more stable and may be produced as follows: This reaction is conducted in the oxidising solvent arsenic pentafluoride . The trichloride anion, [Cl 3 ] , has also been characterised; it is analogous to triiodide . The three fluorides of chlorine form a subset of the interhalogen compounds, all of which are diamagnetic . Some cationic and anionic derivatives are known, such as ClF 2 , ClF 4 , ClF 2 , and Cl 2 F . Some pseudohalides of chlorine are also known, such as cyanogen chloride (ClCN, linear), chlorine cyanate (ClNCO), chlorine thiocyanate (ClSCN, unlike its oxygen counterpart), and chlorine azide (ClN 3 ). Chlorine monofluoride (ClF)

1848-468: A new major field of research that still continues. Eventual confirmation of the phenomenon of neutrino oscillation led to two Nobel prizes, one to R. Davis , who conceived and led the Homestake experiment and Masatoshi Koshiba of Kamiokande, whose work confirmed it, and one to Takaaki Kajita of Super-Kamiokande and A.B. McDonald of Sudbury Neutrino Observatory for their joint experiment, which confirmed

1980-566: A process analogous to light traveling through a transparent material . This process is not directly observable because it does not produce ionizing radiation , but gives rise to the Mikheyev–Smirnov–Wolfenstein effect . Only a small fraction of the neutrino's energy is transferred to the material. Onia For each neutrino, there also exists a corresponding antiparticle , called an antineutrino , which also has no electric charge and half-integer spin. They are distinguished from

2112-418: A proton, electron, and the smaller neutral particle (now called an electron antineutrino ): Fermi's paper, written in 1934, unified Pauli's neutrino with Paul Dirac 's positron and Werner Heisenberg 's neutron–proton model and gave a solid theoretical basis for future experimental work. By 1934, there was experimental evidence against Bohr's idea that energy conservation is invalid for beta decay: At

2244-519: A reduction in oxidation state , which can also be achieved by reducing a higher chloride using hydrogen or a metal as a reducing agent. This may also be achieved by thermal decomposition or disproportionation as follows: Most metal chlorides with the metal in low oxidation states (+1 to +3) are ionic. Nonmetals tend to form covalent molecular chlorides, as do metals in high oxidation states from +3 and above. Both ionic and covalent chlorides are known for metals in oxidation state +3 (e.g. scandium chloride

2376-408: A result of the increasing molecular weight of the halogens down the group, the density and heats of fusion and vaporisation of chlorine are again intermediate between those of bromine and fluorine, although all their heats of vaporisation are fairly low (leading to high volatility) thanks to their diatomic molecular structure. The halogens darken in colour as the group is descended: thus, while fluorine

2508-482: A separate gaseous substance was recognised by the Brabantian chemist and physician Jan Baptist van Helmont . The element was first studied in detail in 1774 by Swedish chemist Carl Wilhelm Scheele , and he is credited with the discovery. Scheele produced chlorine by reacting MnO 2 (as the mineral pyrolusite ) with HCl: Scheele observed several of the properties of chlorine: the bleaching effect on litmus ,

2640-417: A smaller number of neutrinos than the standard model predicted (the solar neutrino problem ). After detector calibration the amount did not change. This discrepancy has since been explained: such radiochemical neutrino detectors are sensitive only to electron neutrinos, and not to muon neutrinos or tau neutrinos , hence the neutrino oscillation of electron neutrinos emitted from the sun and travelling to

2772-625: A solution of sodium carbonate. The resulting liquid, known as " Eau de Javel " (" Javel water "), was a weak solution of sodium hypochlorite . This process was not very efficient, and alternative production methods were sought. Scottish chemist and industrialist Charles Tennant first produced a solution of calcium hypochlorite ("chlorinated lime"), then solid calcium hypochlorite (bleaching powder). These compounds produced low levels of elemental chlorine and could be more efficiently transported than sodium hypochlorite, which remained as dilute solutions because when purified to eliminate water, it became

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2904-605: A varying superposition of three flavors. Each flavor component thereby oscillates as the neutrino travels, with the flavors varying in relative strengths. The relative flavor proportions when the neutrino interacts represent the relative probabilities for that flavor of interaction to produce the corresponding flavor of charged lepton. There are other possibilities in which neutrinos could oscillate even if they were massless: If Lorentz symmetry were not an exact symmetry, neutrinos could experience Lorentz-violating oscillations . Neutrinos traveling through matter, in general, undergo

3036-400: A very short range, the gravitational interaction is extremely weak due to the very small mass of the neutrino, and neutrinos do not participate in the electromagnetic interaction or the strong interaction . Thus, neutrinos typically pass through normal matter unimpeded and undetected. Weak interactions create neutrinos in one of three leptonic flavors : Each flavor is associated with

3168-416: Is hydrogen chloride , HCl, a major chemical in industry as well as in the laboratory, both as a gas and dissolved in water as hydrochloric acid . It is often produced by burning hydrogen gas in chlorine gas, or as a byproduct of chlorinating hydrocarbons . Another approach is to treat sodium chloride with concentrated sulfuric acid to produce hydrochloric acid, also known as the "salt-cake" process: In

3300-441: Is sodium chlorate , mostly used to make chlorine dioxide to bleach paper pulp. The decomposition of chlorate to chloride and oxygen is a common way to produce oxygen in the laboratory on a small scale. Chloride and chlorate may comproportionate to form chlorine as follows: Perchlorates and perchloric acid (HOClO 3 ) are the most stable oxo-compounds of chlorine, in keeping with the fact that chlorine compounds are most stable when

3432-474: Is a pale yellow gas, chlorine is distinctly yellow-green. This trend occurs because the wavelengths of visible light absorbed by the halogens increase down the group. Specifically, the colour of a halogen, such as chlorine, results from the electron transition between the highest occupied antibonding π g molecular orbital and the lowest vacant antibonding σ u molecular orbital. The colour fades at low temperatures, so that solid chlorine at −195 °C

3564-399: Is a poor solvent, only able to dissolve small molecular compounds such as nitrosyl chloride and phenol , or salts with very low lattice energies such as tetraalkylammonium halides. It readily protonates electrophiles containing lone-pairs or π bonds. Solvolysis , ligand replacement reactions, and oxidations are well-characterised in hydrogen chloride solution: Nearly all elements in

3696-486: Is a very poor conductor of electricity, and indeed its conductivity is so low as to be practically unmeasurable. Chlorine has two stable isotopes, Cl and Cl. These are its only two natural isotopes occurring in quantity, with Cl making up 76% of natural chlorine and Cl making up the remaining 24%. Both are synthesised in stars in the oxygen-burning and silicon-burning processes . Both have nuclear spin 3/2+ and thus may be used for nuclear magnetic resonance , although

3828-432: Is a very strong fluorinating agent, although it is still not as effective as chlorine trifluoride. Only a few specific stoichiometric reactions have been characterised. Arsenic pentafluoride and antimony pentafluoride form ionic adducts of the form [ClF 4 ] [MF 6 ] (M = As, Sb) and water reacts vigorously as follows: The product, chloryl fluoride , is one of the five known chlorine oxide fluorides. These range from

3960-442: Is a weak ligand, weaker than water, a few compounds involving coordinated ClO 4 are known. The Table below presents typical oxidation states for chlorine element as given in the secondary schools or colleges. There are more complex chemical compounds, the structure of which can only be explained using modern quantum chemical methods, for example, cluster technetium chloride [(CH 3 ) 4 N] 3 [Tc 6 Cl 14 ], in which 6 of

4092-501: Is almost colourless. Like solid bromine and iodine, solid chlorine crystallises in the orthorhombic crystal system , in a layered lattice of Cl 2 molecules. The Cl–Cl distance is 198 pm (close to the gaseous Cl–Cl distance of 199 pm) and the Cl···Cl distance between molecules is 332 pm within a layer and 382 pm between layers (compare the van der Waals radius of chlorine, 180 pm). This structure means that chlorine

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4224-468: Is also a probe of whether neutrinos are Majorana particles , since there should be a different number of cosmic neutrinos detected in either the Dirac or Majorana case. Neutrinos can interact with a nucleus, changing it to another nucleus. This process is used in radiochemical neutrino detectors . In this case, the energy levels and spin states within the target nucleus have to be taken into account to estimate

4356-472: Is also produced when photolysing the solid at −78 °C: it is a dark brown solid that explodes below 0 °C. The ClO radical leads to the depletion of atmospheric ozone and is thus environmentally important as follows: Chlorine perchlorate (ClOClO 3 ) is a pale yellow liquid that is less stable than ClO 2 and decomposes at room temperature to form chlorine, oxygen, and dichlorine hexoxide (Cl 2 O 6 ). Chlorine perchlorate may also be considered

4488-625: Is an extremely reactive element and a strong oxidising agent : among the elements, it has the highest electron affinity and the third-highest electronegativity on the revised Pauling scale , behind only oxygen and fluorine. Chlorine played an important role in the experiments conducted by medieval alchemists , which commonly involved the heating of chloride salts like ammonium chloride ( sal ammoniac ) and sodium chloride ( common salt ), producing various chemical substances containing chlorine such as hydrogen chloride , mercury(II) chloride (corrosive sublimate), and aqua regia . However,

4620-493: Is conventionally called the "normal hierarchy", while in the "inverted hierarchy", the opposite would hold. Several major experimental efforts are underway to help establish which is correct. A neutrino created in a specific flavor eigenstate is in an associated specific quantum superposition of all three mass eigenstates. The three masses differ so little that they cannot possibly be distinguished experimentally within any practical flight path. The proportion of each mass state in

4752-658: Is even more unstable and cannot be isolated or concentrated without decomposition: it is known from the decomposition of aqueous chlorine dioxide. However, sodium chlorite is a stable salt and is useful for bleaching and stripping textiles, as an oxidising agent, and as a source of chlorine dioxide. Chloric acid (HOClO 2 ) is a strong acid that is quite stable in cold water up to 30% concentration, but on warming gives chlorine and chlorine dioxide. Evaporation under reduced pressure allows it to be concentrated further to about 40%, but then it decomposes to perchloric acid, chlorine, oxygen, water, and chlorine dioxide. Its most important salt

4884-887: Is extremely dangerous, and poisonous to most living organisms. As a chemical warfare agent, chlorine was first used in World War ;I as a poison gas weapon. In the form of chloride ions , chlorine is necessary to all known species of life. Other types of chlorine compounds are rare in living organisms, and artificially produced chlorinated organics range from inert to toxic. In the upper atmosphere , chlorine-containing organic molecules such as chlorofluorocarbons have been implicated in ozone depletion . Small quantities of elemental chlorine are generated by oxidation of chloride ions in neutrophils as part of an immune system response against bacteria. The most common compound of chlorine, sodium chloride, has been known since ancient times; archaeologists have found evidence that rock salt

5016-551: Is extremely thermally stable, and is sold commercially in 500-gram steel lecture bottles. It is a colourless gas that melts at −155.6 °C and boils at −100.1 °C. It may be produced by the reaction of its elements at 225 °C, though it must then be separated and purified from chlorine trifluoride and its reactants. Its properties are mostly intermediate between those of chlorine and fluorine. It will react with many metals and nonmetals from room temperature and above, fluorinating them and liberating chlorine. It will also act as

5148-460: Is important to understand because many neutrinos emitted by fusion in the Sun pass through the dense matter in the solar core (where essentially all solar fusion takes place) on their way to detectors on Earth. Starting in 1998, experiments began to show that solar and atmospheric neutrinos change flavors (see Super-Kamiokande and Sudbury Neutrino Observatory ). This resolved the solar neutrino problem:

5280-515: Is less reactive than fluorine and more reactive than bromine. It is also a weaker oxidising agent than fluorine, but a stronger one than bromine. Conversely, the chloride ion is a weaker reducing agent than bromide, but a stronger one than fluoride. It is intermediate in atomic radius between fluorine and bromine, and this leads to many of its atomic properties similarly continuing the trend from iodine to bromine upward, such as first ionisation energy , electron affinity , enthalpy of dissociation of

5412-442: Is less than +1.395 V, it would be expected that chlorine should be able to oxidise water to oxygen and hydrochloric acid. However, the kinetics of this reaction are unfavorable, and there is also a bubble overpotential effect to consider, so that electrolysis of aqueous chloride solutions evolves chlorine gas and not oxygen gas, a fact that is very useful for the industrial production of chlorine. The simplest chlorine compound

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5544-479: Is low, it has a small liquid range, its dielectric constant is low and it does not dissociate appreciably into H 2 Cl and HCl 2 ions – the latter, in any case, are much less stable than the bifluoride ions ( HF 2 ) due to the very weak hydrogen bonding between hydrogen and chlorine, though its salts with very large and weakly polarising cations such as Cs and NR 4 (R = Me , Et , Bu ) may still be isolated. Anhydrous hydrogen chloride

5676-437: Is made by reacting anhydrous sodium perchlorate or barium perchlorate with concentrated hydrochloric acid, filtering away the chloride precipitated and distilling the filtrate to concentrate it. Anhydrous perchloric acid is a colourless mobile liquid that is sensitive to shock that explodes on contact with most organic compounds, sets hydrogen iodide and thionyl chloride on fire and even oxidises silver and gold. Although it

5808-427: Is mostly ionic, but aluminium chloride is not). Silver chloride is very insoluble in water and is thus often used as a qualitative test for chlorine. Although dichlorine is a strong oxidising agent with a high first ionisation energy, it may be oxidised under extreme conditions to form the [Cl 2 ] cation. This is very unstable and has only been characterised by its electronic band spectrum when produced in

5940-533: Is no experimental evidence for a non-zero magnetic moment in neutrinos. Weak interactions create neutrinos in one of three leptonic flavors : electron neutrinos ( ν e ), muon neutrinos ( ν μ ), or tau neutrinos ( ν τ ), associated with the corresponding charged leptons, the electron ( e ), muon ( μ ), and tau ( τ ), respectively. Although neutrinos were long believed to be massless, it

6072-456: Is now known that there are three discrete neutrino masses; each neutrino flavor state is a linear combination of the three discrete mass eigenstates. Although only differences of squares of the three mass values are known as of 2016, experiments have shown that these masses are tiny compared to any other particle. From cosmological measurements, it has been calculated that the sum of the three neutrino masses must be less than one-millionth that of

6204-415: Is one of the most reactive elements. Chlorine is a weaker oxidising agent than fluorine but a stronger one than bromine or iodine. This can be seen from the standard electrode potentials of the X 2 /X couples (F, +2.866  V; Cl, +1.395 V; Br, +1.087  V; I, +0.615 V; At , approximately +0.3  V). However, this trend is not shown in the bond energies because fluorine

6336-400: Is present in solid crystalline hydrogen chloride at low temperatures, similar to the hydrogen fluoride structure, before disorder begins to prevail as the temperature is raised. Hydrochloric acid is a strong acid (p K a = −7) because the hydrogen bonds to chlorine are too weak to inhibit dissociation. The HCl/H 2 O system has many hydrates HCl· n H 2 O for n = 1, 2, 3, 4, and 6. Beyond

6468-419: Is produced in the atmosphere by spallation of Ar by interactions with cosmic ray protons . In the top meter of the lithosphere , Cl is generated primarily by thermal neutron activation of Cl and spallation of K and Ca . In the subsurface environment, muon capture by Ca becomes more important as a way to generate Cl. Chlorine is intermediate in reactivity between fluorine and bromine, and

6600-401: Is quite slow at temperatures below 70 °C in spite of the very favourable equilibrium constant of 10 . The chlorate ions may themselves disproportionate to form chloride and perchlorate (4 ClO 3 ⇌ Cl + 3 ClO 4 ) but this is still very slow even at 100 °C despite the very favourable equilibrium constant of 10 . The rates of reaction for the chlorine oxyanions increases as

6732-510: Is singular due to its small size, low polarisability, and inability to show hypervalence . As another difference, chlorine has a significant chemistry in positive oxidation states while fluorine does not. Chlorination often leads to higher oxidation states than bromination or iodination but lower oxidation states than fluorination. Chlorine tends to react with compounds including M–M, M–H, or M–C bonds to form M–Cl bonds. Given that E°( ⁠ 1 / 2 ⁠ O 2 /H 2 O) = +1.229 V, which

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6864-567: Is stable to hydrolysis; otherwise, the possibilities include high-temperature oxidative chlorination of the element with chlorine or hydrogen chloride, high-temperature chlorination of a metal oxide or other halide by chlorine, a volatile metal chloride, carbon tetrachloride , or an organic chloride. For instance, zirconium dioxide reacts with chlorine at standard conditions to produce zirconium tetrachloride , and uranium trioxide reacts with hexachloropropene when heated under reflux to give uranium tetrachloride . The second example also involves

6996-553: Is the anhydride of perchloric acid (HClO 4 ) and can readily be obtained from it by dehydrating it with phosphoric acid at −10 °C and then distilling the product at −35 °C and 1 mmHg. It is a shock-sensitive, colourless oily liquid. It is the least reactive of the chlorine oxides, being the only one to not set organic materials on fire at room temperature. It may be dissolved in water to regenerate perchloric acid or in aqueous alkalis to regenerate perchlorates. However, it thermally decomposes explosively by breaking one of

7128-430: Is the anhydride. It is thus an effective bleach and is mostly used to make hypochlorites . It explodes on heating or sparking or in the presence of ammonia gas. Chlorine dioxide (ClO 2 ) was the first chlorine oxide to be discovered in 1811 by Humphry Davy . It is a yellow paramagnetic gas (deep-red as a solid or liquid), as expected from its having an odd number of electrons: it is stable towards dimerisation due to

7260-472: Is usually made by reaction of chlorine dioxide with oxygen. Despite attempts to rationalise it as the dimer of ClO 3 , it reacts more as though it were chloryl perchlorate, [ClO 2 ] [ClO 4 ] , which has been confirmed to be the correct structure of the solid. It hydrolyses in water to give a mixture of chloric and perchloric acids: the analogous reaction with anhydrous hydrogen fluoride does not proceed to completion. Dichlorine heptoxide (Cl 2 O 7 )

7392-475: The 1995 Nobel Prize . In this experiment, now known as the Cowan–Reines neutrino experiment , antineutrinos created in a nuclear reactor by beta decay reacted with protons to produce neutrons and positrons: The positron quickly finds an electron, and they annihilate each other. The two resulting gamma rays (γ) are detectable. The neutron can be detected by its capture on an appropriate nucleus, releasing

7524-544: The Italian Abruzzo province, near L'Aquila , and situated inside the 2912-metre-high Gran Sasso mountain. Its place under a depth of rock equivalent of 3200 metres of water was important to shield from cosmic rays . This laboratory is accessible by a highway A-24, which runs through the mountain. The 54-m detector tank was filled with 101 tons of gallium trichloride - hydrochloric acid solution, which contained 30.3 tons of gallium. The gallium in this solution acted as

7656-451: The Solvay conference of that year, measurements of the energy spectra of beta particles (electrons) were reported, showing that there is a strict limit on the energy of electrons from each type of beta decay. Such a limit is not expected if the conservation of energy is invalid, in which case any amount of energy would be statistically available in at least a few decays. The natural explanation of

7788-509: The Standard Model (see table at right). The current best measurement of the number of neutrino types comes from observing the decay of the Z boson . This particle can decay into any light neutrino and its antineutrino, and the more available types of light neutrinos, the shorter the lifetime of the Z ;boson. Measurements of the Z lifetime have shown that three light neutrino flavors couple to

7920-515: The cosmic neutrino background (CNB). R. Davis and M. Koshiba were jointly awarded the 2002 Nobel Prize in Physics. Both conducted pioneering work on solar neutrino detection, and Koshiba's work also resulted in the first real-time observation of neutrinos from the SN 1987A supernova in the nearby Large Magellanic Cloud . These efforts marked the beginning of neutrino astronomy . SN 1987A represents

8052-515: The muon neutrino (already hypothesised with the name neutretto ), which earned them the 1988 Nobel Prize in Physics . When the third type of lepton, the tau , was discovered in 1975 at the Stanford Linear Accelerator Center , it was also expected to have an associated neutrino (the tau neutrino). The first evidence for this third neutrino type came from the observation of missing energy and momentum in tau decays analogous to

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8184-473: The neutron activation of natural chlorine. The most stable chlorine radioisotope is Cl. The primary decay mode of isotopes lighter than Cl is electron capture to isotopes of sulfur ; that of isotopes heavier than Cl is beta decay to isotopes of argon ; and Cl may decay by either mode to stable S or Ar. Cl occurs in trace quantities in nature as a cosmogenic nuclide in a ratio of about (7–10) × 10 to 1 with stable chlorine isotopes: it

8316-483: The noble gases xenon and radon do not escape fluorination. An impermeable fluoride layer is formed by sodium , magnesium , aluminium , zinc , tin , and silver , which may be removed by heating. Nickel , copper, and steel containers are usually used due to their great resistance to attack by chlorine trifluoride, stemming from the formation of an unreactive layer of metal fluoride. Its reaction with hydrazine to form hydrogen fluoride, nitrogen, and chlorine gases

8448-405: The proton and the electron . He considered that the new particle was emitted from the nucleus together with the electron or beta particle in the process of beta decay and had a mass similar to the electron. James Chadwick discovered a much more massive neutral nuclear particle in 1932 and named it a neutron also, leaving two kinds of particles with the same name. The word "neutrino" entered

8580-414: The 14 chlorine atoms are formally divalent, and oxidation states are fractional. In addition, all the above chemical regularities are valid for "normal" or close to normal conditions, while at ultra-high pressures (for example, in the cores of large planets), chlorine can exhibit an oxidation state of -3, forming a Na3Cl compound with sodium, which does not fit into traditional concepts of chemistry. Like

8712-535: The 1820s, in France, long before the establishment of the germ theory of disease . This practice was pioneered by Antoine-Germain Labarraque , who adapted Berthollet's "Javel water" bleach and other chlorine preparations. Elemental chlorine has since served a continuous function in topical antisepsis (wound irrigation solutions and the like) and public sanitation, particularly in swimming and drinking water. Chlorine gas

8844-449: The 2015 Nobel Prize for Physics for their landmark finding, theoretical and experimental, that neutrinos can change flavors. As well as specific sources, a general background level of neutrinos is expected to pervade the universe, theorized to occur due to two main sources. Around 1 second after the Big Bang , neutrinos decoupled, giving rise to a background level of neutrinos known as

8976-521: The Earth's crust is in the form of ionic chloride compounds, which includes table salt. It is the second-most abundant halogen (after fluorine) and 20th most abundant element in Earth's crust. These crystal deposits are nevertheless dwarfed by the huge reserves of chloride in seawater. Elemental chlorine is commercially produced from brine by electrolysis , predominantly in the chloralkali process . The high oxidising potential of elemental chlorine led to

9108-537: The German and Dutch names of oxygen : sauerstoff or zuurstof , both translating into English as acid substance ), so a number of chemists, including Claude Berthollet , suggested that Scheele's dephlogisticated muriatic acid air must be a combination of oxygen and the yet undiscovered element, muriaticum . In 1809, Joseph Louis Gay-Lussac and Louis-Jacques Thénard tried to decompose dephlogisticated muriatic acid air by reacting it with charcoal to release

9240-463: The Greek letter ν ) is an elementary particle that interacts via the weak interaction and gravity . The neutrino is so named because it is electrically neutral and because its rest mass is so small ( -ino ) that it was long thought to be zero . The rest mass of the neutrino is much smaller than that of the other known elementary particles (excluding massless particles ). The weak force has

9372-439: The Greek word χλωρος ( chlōros , "green-yellow"), in reference to its colour. The name " halogen ", meaning "salt producer", was originally used for chlorine in 1811 by Johann Salomo Christoph Schweigger . This term was later used as a generic term to describe all the elements in the chlorine family (fluorine, bromine, iodine), after a suggestion by Jöns Jakob Berzelius in 1826. In 1823, Michael Faraday liquefied chlorine for

9504-496: The X 2 molecule (X = Cl, Br, I), ionic radius, and X–X bond length. (Fluorine is anomalous due to its small size.) All four stable halogens experience intermolecular van der Waals forces of attraction, and their strength increases together with the number of electrons among all homonuclear diatomic halogen molecules. Thus, the melting and boiling points of chlorine are intermediate between those of fluorine and bromine: chlorine melts at −101.0 °C and boils at −34.0 °C. As

9636-530: The Z. The correspondence between the six quarks in the Standard Model and the six leptons, among them the three neutrinos, suggests to physicists' intuition that there should be exactly three types of neutrino. There are several active research areas involving the neutrino with aspirations of finding: International scientific collaborations install large neutrino detectors near nuclear reactors or in neutrino beams from particle accelerators to better constrain

9768-525: The beta decay leading to the discovery of the electron neutrino. The first detection of tau neutrino interactions was announced in 2000 by the DONUT collaboration at Fermilab ; its existence had already been inferred by both theoretical consistency and experimental data from the Large Electron–Positron Collider . In the 1960s, the now-famous Homestake experiment made the first measurement of

9900-471: The beta decay spectrum as first measured in 1934 was that only a limited (and conserved) amount of energy was available, and a new particle was sometimes taking a varying fraction of this limited energy, leaving the rest for the beta particle. Pauli made use of the occasion to publicly emphasize that the still-undetected "neutrino" must be an actual particle. The first evidence of the reality of neutrinos came in 1938 via simultaneous cloud-chamber measurements of

10032-606: The central Cl–O bonds, producing the radicals ClO 3 and ClO 4 which immediately decompose to the elements through intermediate oxides. Chlorine forms four oxoacids: hypochlorous acid (HOCl), chlorous acid (HOClO), chloric acid (HOClO 2 ), and perchloric acid (HOClO 3 ). As can be seen from the redox potentials given in the adjacent table, chlorine is much more stable towards disproportionation in acidic solutions than in alkaline solutions: The hypochlorite ions also disproportionate further to produce chloride and chlorate (3 ClO ⇌ 2 Cl + ClO 3 ) but this reaction

10164-424: The chlorine atom is in its lowest (−1) or highest (+7) possible oxidation states. Perchloric acid and aqueous perchlorates are vigorous and sometimes violent oxidising agents when heated, in stark contrast to their mostly inactive nature at room temperature due to the high activation energies for these reactions for kinetic reasons. Perchlorates are made by electrolytically oxidising sodium chlorate, and perchloric acid

10296-409: The concept. For the case of neutrinos this theory has gained popularity as it can be used, in combination with the seesaw mechanism , to explain why neutrino masses are so small compared to those of the other elementary particles, such as electrons or quarks. Majorana neutrinos would have the property that the neutrino and antineutrino could be distinguished only by chirality; what experiments observe as

10428-461: The context of preventing the proliferation of nuclear weapons . Because antineutrinos and neutrinos are neutral particles, it is possible that they are the same particle. Rather than conventional Dirac fermions , neutral particles can be another type of spin  ⁠ 1  / 2 ⁠ particle called Majorana particles , named after the Italian physicist Ettore Majorana who first proposed

10560-526: The correspondingly named charged lepton . Although neutrinos were long believed to be massless, it is now known that there are three discrete neutrino masses with different tiny values (the smallest of which could even be zero ), but the three masses do not uniquely correspond to the three flavors: A neutrino created with a specific flavor is a specific mixture of all three mass states (a quantum superposition ). Similar to some other neutral particles , neutrinos oscillate between different flavors in flight as

10692-429: The dark. Crystalline clathrate hydrates ClO 2 · n H 2 O ( n ≈ 6–10) separate out at low temperatures. However, in the presence of light, these solutions rapidly photodecompose to form a mixture of chloric and hydrochloric acids. Photolysis of individual ClO 2 molecules result in the radicals ClO and ClOO, while at room temperature mostly chlorine, oxygen, and some ClO 3 and Cl 2 O 6 are produced. Cl 2 O 3

10824-424: The deadly effect on insects, the yellow-green colour, and the smell similar to aqua regia . He called it " dephlogisticated muriatic acid air " since it is a gas (then called "airs") and it came from hydrochloric acid (then known as "muriatic acid"). He failed to establish chlorine as an element. Common chemical theory at that time held that an acid is a compound that contains oxygen (remnants of this survive in

10956-576: The delocalisation of the unpaired electron. It explodes above −40 °C as a liquid and under pressure as a gas and therefore must be made at low concentrations for wood-pulp bleaching and water treatment. It is usually prepared by reducing a chlorate as follows: Its production is thus intimately linked to the redox reactions of the chlorine oxoacids. It is a strong oxidising agent, reacting with sulfur , phosphorus , phosphorus halides, and potassium borohydride . It dissolves exothermically in water to form dark-green solutions that very slowly decompose in

11088-574: The development of commercial bleaches and disinfectants , and a reagent for many processes in the chemical industry. Chlorine is used in the manufacture of a wide range of consumer products, about two-thirds of them organic chemicals such as polyvinyl chloride (PVC), many intermediates for the production of plastics , and other end products which do not contain the element. As a common disinfectant, elemental chlorine and chlorine-generating compounds are used more directly in swimming pools to keep them sanitary . Elemental chlorine at high concentration

11220-476: The earth accounts for the discrepancy. Results from GALLEX together with SAGE and later confirmed by the BEST experiment have reported a deficit in the expected decay of 71 Ga + ν e → e − + 71 Ge {\displaystyle {}^{71}{\text{Ga}}+\nu _{e}\rightarrow e^{-}+{}^{71}{\text{Ge}}} that has been named

11352-417: The electron and the recoil of the nucleus. In 1942, Wang Ganchang first proposed the use of beta capture to experimentally detect neutrinos. In the 20 July 1956 issue of Science , Clyde Cowan , Frederick Reines , Francis B. "Kiko" Harrison, Herald W. Kruse, and Austin D. McGuire published confirmation that they had detected the neutrino, a result that was rewarded almost forty years later with

11484-406: The electron neutrino, with other approaches to this problem in the planning stages. Chlorine Chlorine is a chemical element ; it has symbol Cl and atomic number 17. The second-lightest of the halogens , it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is a yellow-green gas at room temperature. It

11616-728: The electron neutrino. Neutrinos are fermions with spin of ⁠ 1  / 2 ⁠ . For each neutrino, there also exists a corresponding antiparticle , called an antineutrino , which also has spin of ⁠ 1  / 2 ⁠ and no electric charge. Antineutrinos are distinguished from neutrinos by having opposite-signed lepton number and weak isospin , and right-handed instead of left-handed chirality. To conserve total lepton number (in nuclear beta decay), electron neutrinos only appear together with positrons (anti-electrons) or electron-antineutrinos, whereas electron antineutrinos only appear with electrons or electron neutrinos. Neutrinos are created by various radioactive decays ;

11748-405: The electron neutrinos produced in the Sun had partly changed into other flavors which the experiments could not detect. Although individual experiments, such as the set of solar neutrino experiments, are consistent with non-oscillatory mechanisms of neutrino flavor conversion, taken altogether, neutrino experiments imply the existence of neutrino oscillations. Especially relevant in this context are

11880-451: The electron. More formally, neutrino flavor eigenstates (creation and annihilation combinations) are not the same as the neutrino mass eigenstates (simply labeled "1", "2", and "3"). As of 2024, it is not known which of these three is the heaviest. The neutrino mass hierarchy consists of two possible configurations. In analogy with the mass hierarchy of the charged leptons, the configuration with mass 2 being lighter than mass 3

12012-600: The existence of all three neutrino flavors and found no deficit. A practical method for investigating neutrino oscillations was first suggested by Bruno Pontecorvo in 1957 using an analogy with kaon oscillations; over the subsequent 10 years, he developed the mathematical formalism and the modern formulation of vacuum oscillations. In 1985 Stanislav Mikheyev and Alexei Smirnov (expanding on 1978 work by Lincoln Wolfenstein ) noted that flavor oscillations can be modified when neutrinos propagate through matter. This so-called Mikheyev–Smirnov–Wolfenstein effect (MSW effect)

12144-447: The first time, and demonstrated that what was then known as "solid chlorine" had a structure of chlorine hydrate (Cl 2 ·H 2 O). Chlorine gas was first used by French chemist Claude Berthollet to bleach textiles in 1785. Modern bleaches resulted from further work by Berthollet, who first produced sodium hypochlorite in 1789 in his laboratory in the town of Javel (now part of Paris , France), by passing chlorine gas through

12276-482: The first two. Chlorine has the electron configuration [Ne]3s 3p , with the seven electrons in the third and outermost shell acting as its valence electrons . Like all halogens, it is thus one electron short of a full octet, and is hence a strong oxidising agent, reacting with many elements in order to complete its outer shell. Corresponding to periodic trends , it is intermediate in electronegativity between fluorine and bromine (F: 3.98, Cl: 3.16, Br: 2.96, I: 2.66), and

12408-477: The flux of electron neutrinos arriving from the core of the Sun and found a value that was between one third and one half the number predicted by the Standard Solar Model . This discrepancy, which became known as the solar neutrino problem , remained unresolved for some thirty years, while possible problems with both the experiment and the solar model were investigated, but none could be found. Eventually, it

12540-399: The following list is not exhaustive, but includes some of those processes: The majority of neutrinos which are detected about the Earth are from nuclear reactions inside the Sun. At the surface of the Earth, the flux is about 65 billion ( 6.5 × 10 ) solar neutrinos , per second per square centimeter. Neutrinos can be used for tomography of the interior of the Earth. The neutrino

12672-538: The free element muriaticum (and carbon dioxide). They did not succeed and published a report in which they considered the possibility that dephlogisticated muriatic acid air is an element, but were not convinced. In 1810, Sir Humphry Davy tried the same experiment again, and concluded that the substance was an element, and not a compound. He announced his results to the Royal Society on 15 November that year. At that time, he named this new element "chlorine", from

12804-930: The gallium anomaly . The first solar neutrino detection, the Homestake Experiment , used chlorine -37 to detect neutrinos with energies down to 814 keV. After the end of GALLEX its successor project, the Gallium Neutrino Observatory or G.N.O., was started at LNGS in April 1998. The project continued until 2003. A similar experiment detecting solar neutrinos using liquid gallium-71 was the Russian-American Gallium Experiment SAGE . 42°25′14″N 13°30′59″E  /  42.42056°N 13.51639°E  / 42.42056; 13.51639 Neutrino A neutrino ( / nj uː ˈ t r iː n oʊ / new- TREE -noh ; denoted by

12936-606: The gaseous products were discarded, and hydrogen chloride may have been produced many times before it was discovered that it can be put to chemical use. One of the first such uses was the synthesis of mercury(II) chloride (corrosive sublimate), whose production from the heating of mercury either with alum and ammonium chloride or with vitriol and sodium chloride was first described in the De aluminibus et salibus ("On Alums and Salts", an eleventh- or twelfth century Arabic text falsely attributed to Abu Bakr al-Razi and translated into Latin in

13068-453: The heaviest elements beyond bismuth ); and having an electronegativity higher than chlorine's ( oxygen and fluorine ) so that the resultant binary compounds are formally not chlorides but rather oxides or fluorides of chlorine. Even though nitrogen in NCl 3 is bearing a negative charge, the compound is usually called nitrogen trichloride . Chlorination of metals with Cl 2 usually leads to

13200-593: The hydrogen nuclei in the water molecules. A hydrogen nucleus is a single proton, so simultaneous nuclear interactions, which would occur within a heavier nucleus, do not need to be considered for the detection experiment. Within a cubic meter of water placed right outside a nuclear reactor, only relatively few such interactions can be recorded, but the setup is now used for measuring the reactor's plutonium production rate. Very much like neutrons do in nuclear reactors , neutrinos can induce fission reactions within heavy nuclei . So far, this reaction has not been measured in

13332-513: The initial state, then the final state has only matched lepton and anti-lepton pairs: electron neutrinos appear in the final state together with only positrons (anti-electrons) or electron antineutrinos, and electron antineutrinos with electrons or electron neutrinos. Antineutrinos are produced in nuclear beta decay together with a beta particle (in beta decay a neutron decays into a proton, electron, and antineutrino). All antineutrinos observed thus far had right-handed helicity (i.e., only one of

13464-455: The laboratory, hydrogen chloride gas may be made by drying the acid with concentrated sulfuric acid. Deuterium chloride, DCl, may be produced by reacting benzoyl chloride with heavy water (D 2 O). At room temperature, hydrogen chloride is a colourless gas, like all the hydrogen halides apart from hydrogen fluoride , since hydrogen cannot form strong hydrogen bonds to the larger electronegative chlorine atom; however, weak hydrogen bonding

13596-500: The main building commemorates the discovery. The experiments also implemented a primitive neutrino astronomy and looked at issues of neutrino physics and weak interactions. The antineutrino discovered by Clyde Cowan and Frederick Reines was the antiparticle of the electron neutrino. In 1962, Leon M. Lederman , Melvin Schwartz , and Jack Steinberger showed that more than one type of neutrino exists by first detecting interactions of

13728-563: The most reactive chemical compounds known, the list of elements it sets on fire is diverse, containing hydrogen , potassium , phosphorus , arsenic , antimony , sulfur , selenium , tellurium , bromine , iodine , and powdered molybdenum , tungsten , rhodium , iridium , and iron . It will also ignite water, along with many substances which in ordinary circumstances would be considered chemically inert such as asbestos , concrete, glass, and sand. When heated, it will even corrode noble metals as palladium , platinum , and gold , and even

13860-794: The multiple bonds on alkenes and alkynes as well, giving di- or tetrachloro compounds. However, due to the expense and reactivity of chlorine, organochlorine compounds are more commonly produced by using hydrogen chloride, or with chlorinating agents such as phosphorus pentachloride (PCl 5 ) or thionyl chloride (SOCl 2 ). The last is very convenient in the laboratory because all side products are gaseous and do not have to be distilled out. Many organochlorine compounds have been isolated from natural sources ranging from bacteria to humans. Chlorinated organic compounds are found in nearly every class of biomolecules including alkaloids , terpenes , amino acids , flavonoids , steroids , and fatty acids . Organochlorides, including dioxins , are produced in

13992-560: The nature of free chlorine gas as a separate substance was only recognised around 1630 by Jan Baptist van Helmont . Carl Wilhelm Scheele wrote a description of chlorine gas in 1774, supposing it to be an oxide of a new element. In 1809, chemists suggested that the gas might be a pure element, and this was confirmed by Sir Humphry Davy in 1810, who named it after the Ancient Greek χλωρός ( khlōrós , "pale green") because of its colour. Because of its great reactivity, all chlorine in

14124-504: The neutrino masses and the values for the magnitude and rates of oscillations between neutrino flavors. These experiments are thereby searching for the existence of CP violation in the neutrino sector; that is, whether or not the laws of physics treat neutrinos and antineutrinos differently. The KATRIN experiment in Germany began to acquire data in June 2018 to determine the value of the mass of

14256-404: The neutrinos by having opposite signs of lepton number and opposite chirality (and consequently opposite-sign weak isospin). As of 2016, no evidence has been found for any other difference. So far, despite extensive and continuing searches for exceptions, in all observed leptonic processes there has never been any change in total lepton number; for example, if the total lepton number is zero in

14388-578: The only verified detection of neutrinos from a supernova. However, many stars have gone supernova in the universe, leaving a theorized diffuse supernova neutrino background . Neutrinos have half-integer spin ( ⁠ 1  / 2 ⁠ ħ ); therefore they are fermions . Neutrinos are leptons. They have only been observed to interact through the weak force , although it is assumed that they also interact gravitationally. Since they have non-zero mass, theoretical considerations permit neutrinos to interact magnetically, but do not require them to. As yet there

14520-458: The other carbon–halogen bonds, the C–Cl bond is a common functional group that forms part of core organic chemistry . Formally, compounds with this functional group may be considered organic derivatives of the chloride anion. Due to the difference of electronegativity between chlorine (3.16) and carbon (2.55), the carbon in a C–Cl bond is electron-deficient and thus electrophilic . Chlorination modifies

14652-605: The oxidation state of chlorine decreases. The strengths of the chlorine oxyacids increase very quickly as the oxidation state of chlorine increases due to the increasing delocalisation of charge over more and more oxygen atoms in their conjugate bases. Most of the chlorine oxoacids may be produced by exploiting these disproportionation reactions. Hypochlorous acid (HOCl) is highly reactive and quite unstable; its salts are mostly used for their bleaching and sterilising abilities. They are very strong oxidising agents, transferring an oxygen atom to most inorganic species. Chlorous acid (HOClO)

14784-401: The period 1991-1997, the detector measured capture rate of 73.1 SNU ( Solar neutrino units ). The follow-up GNO experiment found the capture rate 62.9. The rate of neutrinos detected by this experiment disagreed with standard solar model predictions. Thanks to the use of gallium, it was the first experiment to observe solar initial pp neutrinos. Another important result was the detection of

14916-406: The periodic table form binary chlorides. The exceptions are decidedly in the minority and stem in each case from one of three causes: extreme inertness and reluctance to participate in chemical reactions (the noble gases , with the exception of xenon in the highly unstable XeCl 2 and XeCl 4 ); extreme nuclear instability hampering chemical investigation before decay and transmutation (many of

15048-418: The physical properties of hydrocarbons in several ways: chlorocarbons are typically denser than water due to the higher atomic weight of chlorine versus hydrogen, and aliphatic organochlorides are alkylating agents because chloride is a leaving group . Alkanes and aryl alkanes may be chlorinated under free-radical conditions, with UV light. However, the extent of chlorination is difficult to control:

15180-409: The probability for an interaction. In general the interaction probability increases with the number of neutrons and protons within a nucleus. It is very hard to uniquely identify neutrino interactions among the natural background of radioactivity. For this reason, in early experiments a special reaction channel was chosen to facilitate the identification: the interaction of an antineutrino with one of

15312-684: The pure flavor states produced has been found to depend profoundly on the flavor. The relationship between flavor and mass eigenstates is encoded in the PMNS matrix . Experiments have established moderate- to low-precision values for the elements of this matrix, with the single complex phase in the matrix being only poorly known, as of 2016. A non-zero mass allows neutrinos to possibly have a tiny magnetic moment ; if so, neutrinos would interact electromagnetically, although no such interaction has ever been observed. Neutrinos oscillate between different flavors in flight. For example, an electron neutrino produced in

15444-529: The reaction is not regioselective and often results in a mixture of various isomers with different degrees of chlorination, though this may be permissible if the products are easily separated. Aryl chlorides may be prepared by the Friedel-Crafts halogenation , using chlorine and a Lewis acid catalyst. The haloform reaction , using chlorine and sodium hydroxide , is also able to generate alkyl halides from methyl ketones, and related compounds. Chlorine adds to

15576-435: The reaction with gallium suitable to the detection of neutrinos emitted in the initial proton fusion reaction of the proton-proton chain reaction , which have a maximum energy of 420 keV. The produced germanium-71 was chemically extracted from the detector, converted to germane (GeH 4 ). Its decay, with a half-life of 11.43 days, was detected by counters. Each detected decay corresponded to one detected neutrino. During

15708-428: The reactor experiment KamLAND and the accelerator experiments such as MINOS . The KamLAND experiment has indeed identified oscillations as the neutrino flavor conversion mechanism involved in the solar electron neutrinos. Similarly MINOS confirms the oscillation of atmospheric neutrinos and gives a better determination of the mass squared splitting. Takaaki Kajita of Japan, and Arthur B. McDonald of Canada, received

15840-910: The scientific vocabulary through Enrico Fermi , who used it during a conference in Paris in July ;1932 and at the Solvay Conference in October ;1933, where Pauli also employed it. The name (the Italian equivalent of "little neutral one") was jokingly coined by Edoardo Amaldi during a conversation with Fermi at the Institute of Physics of via Panisperna in Rome, in order to distinguish this light neutral particle from Chadwick's heavy neutron. In Fermi's theory of beta decay , Chadwick's large neutral particle could decay to

15972-610: The second half of the twelfth century by Gerard of Cremona , 1144–1187). Another important development was the discovery by pseudo-Geber (in the De inventione veritatis , "On the Discovery of Truth", after c. 1300) that by adding ammonium chloride to nitric acid , a strong solvent capable of dissolving gold (i.e., aqua regia ) could be produced. Although aqua regia is an unstable mixture that continually gives off fumes containing free chlorine gas, this chlorine gas appears to have been ignored until c. 1630, when its nature as

16104-481: The spin magnitude being greater than 1/2 results in non-spherical nuclear charge distribution and thus resonance broadening as a result of a nonzero nuclear quadrupole moment and resultant quadrupolar relaxation. The other chlorine isotopes are all radioactive, with half-lives too short to occur in nature primordially . Of these, the most commonly used in the laboratory are Cl ( t 1/2 = 3.0×10  y) and Cl ( t 1/2 = 37.2 min), which may be produced from

16236-437: The sulfur oxides SO 2 and SO 3 to produce ClSO 2 F and ClOSO 2 F respectively. It will also react exothermically with compounds containing –OH and –NH groups, such as water: Chlorine trifluoride (ClF 3 ) is a volatile colourless molecular liquid which melts at −76.3 °C and boils at 11.8  °C. It may be formed by directly fluorinating gaseous chlorine or chlorine monofluoride at 200–300 °C. One of

16368-412: The target for a neutrino-induced nuclear reaction , which transmuted it into germanium through the following reaction: The threshold for neutrino detection by this reaction is very low (233.2 keV), and this is also the reason why gallium was chosen: other reactions (as with chlorine -37) have higher thresholds and are thus unable to detect low-energy neutrinos. In fact, the low energy threshold makes

16500-586: The thermally unstable FClO to the chemically unreactive perchloryl fluoride (FClO 3 ), the other three being FClO 2 , F 3 ClO, and F 3 ClO 2 . All five behave similarly to the chlorine fluorides, both structurally and chemically, and may act as Lewis acids or bases by gaining or losing fluoride ions respectively or as very strong oxidising and fluorinating agents. The chlorine oxides are well-studied in spite of their instability (all of them are endothermic compounds). They are important because they are produced when chlorofluorocarbons undergo photolysis in

16632-449: The two possible spin states has ever been seen), while neutrinos were all left-handed. Antineutrinos were first detected as a result of their interaction with protons in a large tank of water. This was installed next to a nuclear reactor as a controllable source of the antineutrinos (see Cowan–Reines neutrino experiment ). Researchers around the world have begun to investigate the possibility of using antineutrinos for reactor monitoring in

16764-406: The upper atmosphere and cause the destruction of the ozone layer. None of them can be made from directly reacting the elements. Dichlorine monoxide (Cl 2 O) is a brownish-yellow gas (red-brown when solid or liquid) which may be obtained by reacting chlorine gas with yellow mercury(II) oxide . It is very soluble in water, in which it is in equilibrium with hypochlorous acid (HOCl), of which it

16896-556: Was first used as a weapon on April 22, 1915, at the Second Battle of Ypres by the German Army . The effect on the allies was devastating because the existing gas masks were difficult to deploy and had not been broadly distributed. Chlorine is the second halogen , being a nonmetal in group 17 of the periodic table. Its properties are thus similar to fluorine , bromine , and iodine , and are largely intermediate between those of

17028-423: Was postulated first by Wolfgang Pauli in 1930 to explain how beta decay could conserve energy , momentum , and angular momentum ( spin ). In contrast to Niels Bohr , who proposed a statistical version of the conservation laws to explain the observed continuous energy spectra in beta decay , Pauli hypothesized an undetected particle that he called a "neutron", using the same -on ending employed for naming both

17160-404: Was realized that both were actually correct and that the discrepancy between them was due to neutrinos being more complex than was previously assumed. It was postulated that the three neutrinos had nonzero and slightly different masses, and could therefore oscillate into undetectable flavors on their flight to the Earth. This hypothesis was investigated by a new series of experiments, thereby opening

17292-619: Was used as early as 3000 BC and brine as early as 6000 BC. Around 900, the authors of the Arabic writings attributed to Jabir ibn Hayyan (Latin: Geber) and the Persian physician and alchemist Abu Bakr al-Razi ( c. 865–925, Latin: Rhazes) were experimenting with sal ammoniac ( ammonium chloride ), which when it was distilled together with vitriol (hydrated sulfates of various metals) produced hydrogen chloride . However, it appears that in these early experiments with chloride salts ,

17424-434: Was used in experimental rocket engine, but has problems largely stemming from its extreme hypergolicity resulting in ignition without any measurable delay. Today, it is mostly used in nuclear fuel processing, to oxidise uranium to uranium hexafluoride for its enriching and to separate it from plutonium , as well as in the semiconductor industry, where it is used to clean chemical vapor deposition chambers. It can act as

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