Legend
50-453: The halogens ( / ˈ h æ l ə dʒ ə n , ˈ h eɪ -, - l oʊ -, - ˌ dʒ ɛ n / ) are a group in the periodic table consisting of six chemically related elements : fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and the radioactive elements astatine (At) and tennessine (Ts), though some authors would exclude tennessine as its chemistry is unknown and is theoretically expected to be more like that of gallium . In
100-412: A family ) is a column of elements in the periodic table of the chemical elements . There are 18 numbered groups in the periodic table; the 14 f-block columns, between groups 2 and 3, are not numbered. The elements in a group have similar physical or chemical characteristics of the outermost electron shells of their atoms (i.e., the same core charge ), because most chemical properties are dominated by
150-483: A heavier halogen. Chlorine and bromine can bond with up to five fluorine atoms, and iodine can bond with up to seven fluorine atoms. Most interhalogen compounds are covalent gases. However, some interhalogens are liquids, such as BrF 3 , and many iodine-containing interhalogens are solids. Many synthetic organic compounds such as plastic polymers , and a few natural ones, contain halogen atoms; these are known as halogenated compounds or organic halides . Chlorine
200-451: A process known as sterilization . Their reactivity is also put to use in bleaching . Sodium hypochlorite , which is produced from chlorine, is the active ingredient of most fabric bleaches, and chlorine-derived bleaches are used in the production of some paper products. Halogen lamps are a type of incandescent lamp using a tungsten filament in bulbs that have small amounts of a halogen, such as iodine or bromine added. This enables
250-435: A protective layer of fluoride on their surface. The high reactivity of fluorine allows some of the strongest bonds possible, especially to carbon. For example, Teflon is fluorine bonded with carbon and is extremely resistant to thermal and chemical attacks and has a high melting point. The stable halogens form homonuclear diatomic molecules . Due to relatively weak intermolecular forces, chlorine and fluorine form part of
300-497: A reaction of a pure halogen with a smaller interhalogen such as ClF . All interhalogens except IF 7 can be produced by directly combining pure halogens in various conditions. Interhalogens are typically more reactive than all diatomic halogen molecules except F 2 because interhalogen bonds are weaker. However, the chemical properties of interhalogens are still roughly the same as those of diatomic halogens. Many interhalogens consist of one or more atoms of fluorine bonding to
350-448: A solution that can be used as a disinfectant or bleach : Bromine has a solubility of 3.41 g per 100 g of water, but it slowly reacts to form hydrogen bromide (HBr) and hypobromous acid (HBrO): Iodine, however, is minimally soluble in water (0.03 g/100 g water at 20 °C) and does not react with it. However, iodine will form an aqueous solution in the presence of iodide ion, such as by addition of potassium iodide (KI), because
400-418: Is a weak acid . All of the hydrogen halides are irritants . Hydrogen fluoride and hydrogen chloride are highly acidic . Hydrogen fluoride is used as an indu strial chemical, and is highly toxic, causing pulmonary edema and damaging cells. Hydrogen chloride is also a dangerous chemical. Breathing in gas with more than fifty parts per million of hydrogen chloride can cause death in humans. Hydrogen bromide
450-538: Is also possible to produce bromine by passing chlorine through seawater and then passing air through the seawater. In 2003, 22,000 metric tons of iodine were produced. Chile produces 40% of all iodine produced, Japan produces 30%, and smaller amounts are produced in Russia and the United States. Until the 1950s, iodine was extracted from kelp . However, in modern times, iodine is produced in other ways. One way that iodine
500-457: Is by far the most abundant of the halogens in seawater, and the only one needed in relatively large amounts (as chloride ions) by humans. For example, chloride ions play a key role in brain function by mediating the action of the inhibitory transmitter GABA and are also used by the body to produce stomach acid. Iodine is needed in trace amounts for the production of thyroid hormones such as thyroxine . Organohalogens are also synthesized through
550-462: Is due to the high electronegativity of the atoms due to their high effective nuclear charge . Because the halogens have seven valence electrons in their outermost energy level, they can gain an electron by reacting with atoms of other elements to satisfy the octet rule . Fluorine is the most reactive of all elements; it is the only element more electronegative than oxygen, it attacks otherwise-inert materials such as glass, and it forms compounds with
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#1732859105405600-469: Is even more toxic and irritating than hydrogen chloride. Breathing in gas with more than thirty parts per million of hydrogen bromide can be lethal to humans. Hydrogen iodide, like other hydrogen halides, is toxic. All the halogens are known to react with sodium to form sodium fluoride , sodium chloride , sodium bromide , sodium iodide , and sodium astatide. Heated sodium's reaction with halogens produces bright-orange flames. Sodium's reaction with chlorine
650-441: Is in the form of: Iron reacts with fluorine, chlorine, and bromine to form iron(III) halides. These reactions are in the form of: However, when iron reacts with iodine, it forms only iron(II) iodide . Iron wool can react rapidly with fluorine to form the white compound iron(III) fluoride even in cold temperatures. When chlorine comes into contact with a heated iron, they react to form the black iron(III) chloride . However, if
700-461: Is named after the US state of Tennessee , where it was synthesized. The halogens fluorine, chlorine, bromine, and iodine are nonmetals ; the chemical properties of the two heaviest group 17 members have not been conclusively investigated. The halogens show trends in chemical bond energy moving from top to bottom of the periodic table column with fluorine deviating slightly. It follows a trend in having
750-590: Is produced is by mixing sulfur dioxide with nitrate ores, which contain some iodates . Iodine is also extracted from natural gas fields. Even though astatine is naturally occurring, it is usually produced by bombarding bismuth with alpha particles. Tennessine is made by using a cyclotron, fusing berkelium-249 and calcium-48 to make tennessine-293 and tennessine-294. Both chlorine and bromine are used as disinfectants for drinking water, swimming pools, fresh wounds, spas, dishes, and surfaces. They kill bacteria and other potentially harmful microorganisms through
800-518: The JINR , Oak Ridge National Laboratory , Lawrence Livermore National Laboratory , and Vanderbilt University successfully bombarded berkelium-249 atoms with calcium-48 atoms to make tennessine. In 1811, the German chemist Johann Schweigger proposed that the name "halogen" – meaning "salt producer", from αλς [hals] "salt" and γενειν [genein] "to beget" – replace the name "chlorine", which had been proposed by
850-585: The Latin word fluere , meaning "to flow", because it was derived from the mineral fluorite , which was used as a flux in metalworking. Chlorine's name comes from the Greek word chloros , meaning "greenish-yellow". Bromine's name comes from the Greek word bromos , meaning "stench". Iodine's name comes from the Greek word iodes , meaning "violet". Astatine's name comes from the Greek word astatos , meaning "unstable". Tennessine
900-582: The electrolysis of brine . Approximately 450,000 metric tons of bromine are produced each year. Fifty percent of all bromine produced is produced in the United States , 35% in Israel , and most of the remainder in China . Historically, bromine was produced by adding sulfuric acid and bleaching powder to natural brine. However, in modern times, bromine is produced by electrolysis, a method invented by Herbert Dow . It
950-639: The nucleophilic abstraction reaction. Polyhalogenated compounds are industrially created compounds substituted with multiple halogens. Many of them are very toxic and bioaccumulate in humans, and have a very wide application range. They include PCBs , PBDEs , and perfluorinated compounds (PFCs), as well as numerous other compounds. Fluorine reacts vigorously with water to produce oxygen (O 2 ) and hydrogen fluoride (HF): Chlorine has maximum solubility of ca. 7.1 g Cl 2 per kg of water at ambient temperature (21 °C). Dissolved chlorine reacts to form hydrochloric acid (HCl) and hypochlorous acid ,
1000-711: The triiodide ion is formed. The table below is a summary of the key physical and atomic properties of the halogens. Data marked with question marks are either uncertain or are estimations partially based on periodic trends rather than observations. Fluorine has one stable and naturally occurring isotope , fluorine-19. However, there are trace amounts in nature of the radioactive isotope fluorine-23, which occurs via cluster decay of protactinium-231 . A total of eighteen isotopes of fluorine have been discovered, with atomic masses ranging from 13 to 31. Chlorine has two stable and naturally occurring isotopes , chlorine-35 and chlorine-37. However, there are trace amounts in nature of
1050-461: The 14 f-block columns remaining unnumbered (together making the 32 columns in the periodic table). Also, trivial names (like halogens ) are common. In history, several sets of group names have been used, based on Roman numberings I–VIII, and "A" and "B" suffixes. Two earlier group number systems exist: CAS ( Chemical Abstracts Service ) and old IUPAC . Both use numerals ( Arabic or Roman ) and letters A and B . Both systems agree on
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#17328591054051100-570: The 1990 edition of the Nomenclature of Inorganic Chemistry . While groups are defined to be columns in the periodic table, as described above, there are also sets of elements named "group" that are not a column: Similar sets: noble metals , coinage metals , precious metals , refractory metals . Joseph Gay-Lussac Too Many Requests If you report this error to the Wikimedia System Administrators, please include
1150-509: The English chemist Humphry Davy . Davy's name for the element prevailed. However, in 1826, the Swedish chemist Baron Jöns Jacob Berzelius proposed the term "halogen" for the elements fluorine, chlorine, and iodine, which produce a sea-salt -like substance when they form a compound with an alkaline metal. The English names of these elements all have the ending -ine . Fluorine's name comes from
1200-670: The correct positioning has been known since 1948 and was twice endorsed by IUPAC in 1988 (together with the 1–18 numbering) and 2021. Groups may also be identified using their topmost element, or have a specific name. For example, group 16 is also described as the "oxygen group" and as the " chalcogens ". An exception is the " iron group ", which usually refers to group 8 , but in chemistry may also mean iron , cobalt , and nickel , or some other set of elements with similar chemical properties. In astrophysics and nuclear physics , it usually refers to iron, cobalt, nickel, chromium , and manganese . Modern group names are numbers 1–18, with
1250-423: The element "dephlogisticated muriatic acid", which is how chlorine was known for 33 years. In 1807, Humphry Davy investigated chlorine and discovered that it is an actual element. Chlorine gas was used as a poisonous gas during World War I . It displaced oxygen in contaminated areas and replaced common oxygenated air with the toxic chlorine gas. The gas would burn human tissue externally and internally, especially
1300-518: The fluorine mineral fluorite are produced each year. Four hundred-thousand metric tons of hydrofluoric acid are made each year. Fluorine gas is made from hydrofluoric acid produced as a by-product in phosphoric acid manufacture. Approximately 15,000 metric tons of fluorine gas are made per year. The mineral halite is the mineral that is most commonly mined for chlorine, but the minerals carnallite and sylvite are also mined for chlorine. Forty million metric tons of chlorine are produced each year by
1350-570: The group known as "elemental gases". The elements become less reactive and have higher melting points as the atomic number increases. The higher melting points are caused by stronger London dispersion forces resulting from more electrons. All of the halogens have been observed to react with hydrogen to form hydrogen halides . For fluorine, chlorine, and bromine, this reaction is in the form of: However, hydrogen iodide and hydrogen astatide can split back into their constituent elements. The hydrogen-halogen reactions get gradually less reactive toward
1400-421: The heavier halogens. A fluorine-hydrogen reaction is explosive even when it is dark and cold. A chlorine-hydrogen reaction is also explosive, but only in the presence of light and heat. A bromine-hydrogen reaction is even less explosive; it is explosive only when exposed to flames. Iodine and astatine only partially react with hydrogen, forming equilibria . All halogens form binary compounds with hydrogen known as
1450-410: The highest bond energy in compounds with other atoms, but it has very weak bonds within the diatomic F 2 molecule. This means that further down group 17 in the periodic table, the reactivity of elements decreases because of the increasing size of the atoms. Halogens are highly reactive , and as such can be harmful or lethal to biological organisms in sufficient quantities. This high reactivity
1500-409: The hydrogen halides: hydrogen fluoride (HF), hydrogen chloride (HCl), hydrogen bromide (HBr), hydrogen iodide (HI), and hydrogen astatide (HAt). All of these compounds form acids when mixed with water. Hydrogen fluoride is the only hydrogen halide that forms hydrogen bonds . Hydrochloric acid, hydrobromic acid, hydroiodic acid, and hydroastatic acid are all strong acids , but hydrofluoric acid
1550-421: The incorporation of halogen atoms into a lead drug candidate results in analogues that are usually more lipophilic and less water-soluble. As a consequence, halogen atoms are used to improve penetration through lipid membranes and tissues. It follows that there is a tendency for some halogenated drugs to accumulate in adipose tissue . Group (periodic table) In chemistry , a group (also known as
Halogen - Misplaced Pages Continue
1600-491: The isotope chlorine-36 , which occurs via spallation of argon-36. A total of 24 isotopes of chlorine have been discovered, with atomic masses ranging from 28 to 51. There are two stable and naturally occurring isotopes of bromine , bromine-79 and bromine-81. A total of 33 isotopes of bromine have been discovered, with atomic masses ranging from 66 to 98. There is one stable and naturally occurring isotope of iodine , iodine-127 . However, there are trace amounts in nature of
1650-470: The lungs, making breathing difficult or impossible depending on the level of contamination. Bromine was discovered in the 1820s by Antoine Jérôme Balard . Balard discovered bromine by passing chlorine gas through a sample of brine . He originally proposed the name muride for the new element, but the French Academy changed the element's name to bromine. Iodine was discovered by Bernard Courtois , who
1700-434: The main states of matter at standard temperature and pressure , though not far above room temperature the same becomes true of groups 1 and 15 , assuming white phosphorus is taken as the standard state. All of the halogens form acids when bonded to hydrogen. Most halogens are typically produced from minerals or salts . The middle halogens—chlorine, bromine, and iodine—are often used as disinfectants . Organobromides are
1750-402: The modern IUPAC nomenclature, this group is known as group 17 . The word "halogen" means "salt former" or "salt maker". When halogens react with metals , they produce a wide range of salts , including calcium fluoride , sodium chloride (common table salt), silver bromide and potassium iodide . The group of halogens is the only periodic table group that contains elements in three of
1800-420: The most important class of flame retardants , while elemental halogens are dangerous and can be toxic. The fluorine mineral fluorospar was known as early as 1529. Early chemists realized that fluorine compounds contain an undiscovered element, but were unable to isolate it. In 1860, George Gore , an English chemist, ran a current of electricity through hydrofluoric acid and probably produced fluorine, but he
1850-419: The numbers. The numbers indicate approximately the highest oxidation number of the elements in that group, and so indicate similar chemistry with other elements with the same numeral. The number proceeds in a linearly increasing fashion for the most part, once on the left of the table, and once on the right (see List of oxidation states of the elements ), with some irregularities in the transition metals. However,
1900-474: The orbital location of the outermost electron. The modern numbering system of "group 1" to "group 18" has been recommended by the International Union of Pure and Applied Chemistry (IUPAC) since 1988. The 1-18 system is based on each atom's s, p and d electrons beyond those in atoms of the preceding noble gas. Two older incompatible naming schemes can assign the same number to different groups depending on
1950-502: The production of lamps that are much smaller than non-halogen incandescent lightbulbs at the same wattage . The gas reduces the thinning of the filament and blackening of the inside of the bulb resulting in a bulb that has a much greater life. Halogen lamps glow at a higher temperature (2800 to 3400 kelvin ) with a whiter colour than other incandescent bulbs. However, this requires bulbs to be manufactured from fused quartz rather than silica glass to reduce breakage. In drug discovery ,
2000-880: The radioactive isotope iodine-129 , which occurs via spallation and from the radioactive decay of uranium in ores. Several other radioactive isotopes of iodine have also been created naturally via the decay of uranium. A total of 38 isotopes of iodine have been discovered, with atomic masses ranging from 108 to 145. There are no stable isotopes of astatine . However, there are four naturally occurring radioactive isotopes of astatine produced via radioactive decay of uranium , neptunium , and plutonium . These isotopes are astatine-215, astatine-217, astatine-218, and astatine-219. A total of 31 isotopes of astatine have been discovered, with atomic masses ranging from 191 to 227. There are no stable isotopes of tennessine . Tennessine has only two known synthetic radioisotopes , tennessine-293 and tennessine-294. Approximately six million metric tons of
2050-399: The reaction conditions are moist, this reaction will instead result in a reddish-brown product. Iron can also react with bromine to form iron(III) bromide . This compound is reddish-brown in dry conditions. Iron's reaction with bromine is less reactive than its reaction with fluorine or chlorine. A hot iron can also react with iodine, but it forms iron(II) iodide. This compound may be gray, but
Halogen - Misplaced Pages Continue
2100-412: The reaction is always contaminated with excess iodine, so it is not known for sure. Iron's reaction with iodine is less vigorous than its reaction with the lighter halogens. Interhalogen compounds are in the form of XY n where X and Y are halogens and n is one, three, five, or seven. Interhalogen compounds contain at most two different halogens. Large interhalogens, such as ClF 3 can be produced by
2150-620: The system being used. The older schemes were used by the Chemical Abstract Service (CAS, more popular in the United States), and by IUPAC before 1988 (more popular in Europe). The system of eighteen groups is generally accepted by the chemistry community, but some dissent exists about membership of elements number 1 and 2 ( hydrogen and helium ). Similar variation on the inner transition metals continues to exist in textbooks, although
2200-498: The two systems use the letters differently. For example, potassium (K) has one valence electron . Therefore, it is located in group 1. Calcium (Ca) is in group 2, for it contains two valence electrons. In the old IUPAC system the letters A and B were designated to the left (A) and right (B) part of the table, while in the CAS system the letters A and B are designated to main group elements (A) and transition elements (B). The old IUPAC system
2250-447: The usually inert noble gases . It is a corrosive and highly toxic gas. The reactivity of fluorine is such that, if used or stored in laboratory glassware, it can react with glass in the presence of small amounts of water to form silicon tetrafluoride (SiF 4 ). Thus, fluorine must be handled with substances such as Teflon (which is itself an organofluorine compound), extremely dry glass, or metals such as copper or steel, which form
2300-421: Was also unsuccessful, as was an attempt in the same year by Walter Minder , who discovered an iodine-like element resulting from beta decay of polonium . Element 85, now named astatine, was produced successfully in 1940 by Dale R. Corson , K.R. Mackenzie , and Emilio G. Segrè , who bombarded bismuth with alpha particles . In 2010, a team led by nuclear physicist Yuri Oganessian involving scientists from
2350-504: Was frequently used in Europe, while the CAS is most common in America. The new IUPAC scheme was developed to replace both systems as they confusingly used the same names to mean different things. The new system simply numbers the groups increasingly from left to right on the standard periodic table. The IUPAC proposal was first circulated in 1985 for public comments, and was later included as part of
2400-441: Was proven to be a new element by Joseph Gay-Lussac . In 1931, Fred Allison claimed to have discovered element 85 with a magneto-optical machine , and named the element Alabamine, but was mistaken. In 1937, Rajendralal De claimed to have discovered element 85 in minerals, and called the element dakine, but he was also mistaken. An attempt at discovering element 85 in 1939 by Horia Hulubei and Yvette Cauchois via spectroscopy
2450-488: Was unable to prove his results at the time. In 1886, Henri Moissan , a chemist in Paris, performed electrolysis on potassium bifluoride dissolved in anhydrous hydrogen fluoride , and successfully isolated fluorine. Hydrochloric acid was known to alchemists and early chemists. However, elemental chlorine was not produced until 1774, when Carl Wilhelm Scheele heated hydrochloric acid with manganese dioxide . Scheele called
2500-424: Was using seaweed ash as part of a process for saltpeter manufacture. Courtois typically boiled the seaweed ash with water to generate potassium chloride . However, in 1811, Courtois added sulfuric acid to his process and found that his process produced purple fumes that condensed into black crystals. Suspecting that these crystals were a new element, Courtois sent samples to other chemists for investigation. Iodine
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