"atom of the compound. Interhalogens containing fluorine are more likely to be volatile than interhalogens containing heavier halogens. Interhalogens with one or three halogens bonded to a central atom are formed by two elements whose electronegativities are not far apart. Interhalogens with five or seven halogens bonded to a central atom are formed by two elements whose sizes are very different. The number of smaller halogens that can bond to a large central halogen is guided by the ratio of the atomic radius of the larger halogen over the atomic radius of the smaller halogen. A number of interhalogens, such"
"Fluorine Fluorine is a chemical element with symbol F and atomic number 9. It is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions. As the most electronegative element, it is extremely reactive, as it reacts with almost all other elements, except for helium and neon. Among the elements, fluorine ranks 24th in universal abundance and 13th in terrestrial abundance. Fluorite, the primary mineral source of fluorine which gave the element its name, was first described in 1529; as it was added to metal ores to lower their melting points for smelting, the"
"than iodine, astatine is the least reactive of the halogens, although its compounds have been synthesized in microscopic amounts and studied as intensively as possible before their radioactive disintegration. The reactions involved have been typically tested with dilute solutions of astatine mixed with larger amounts of iodine. Acting as a carrier, the iodine ensures there is sufficient material for laboratory techniques (such as filtration and precipitation) to work. Like iodine, astatine has been shown to adopt odd-numbered oxidation states ranging from −1 to +7. Only a few compounds with metals have been reported, in the form of astatides of sodium,"
"characteristic odor to rotting eggs and other biological processes. ""Chlorine"" (symbol Cl) is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine. It has the highest electron affinity and the third highest electronegativity of all the elements; for this reason, chlorine is a strong oxidizing agent. The most common compound of chlorine, sodium chloride, has been known since ancient times; however, around 1630, chlorine gas was obtained by the Belgian chemist and physician Jan Baptist van Helmont. The synthesis and characterization of elemental chlorine occurred in 1774"
"and blood before excretion through the kidneys. Dwell time in the body varies greatly by species, with half-lives of days in rodents, and years in humans. High doses of PFOS and PFOA cause cancer and death in newborn rodents but human studies have not established an effect at current exposure levels. Fluorine Fluorine is a chemical element with symbol F and atomic number 9. It is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions. As the most electronegative element, it is extremely reactive, as it reacts with almost all other elements, except"
"Halogen The halogens () are a group in the periodic table consisting of five chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). The artificially created element 117 (tennessine, Ts) may also be a halogen. In the modern IUPAC nomenclature, this group is known as group 17. The symbol X is often used generically to refer to any halogen. The name ""halogen"" means ""salt-producing"". 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"
"other halogens, it is 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, although in keeping with periodic trends, it is the weakest oxidising agent among the stable halogens: it has the lowest electronegativity among them, just 2.66 on the Pauling scale (compare fluorine, chlorine, and bromine at 3.98, 3.16, and 2.96 respectively; astatine continues the trend with an electronegativity of 2.2). Elemental iodine hence forms diatomic molecules with chemical formula I, where two iodine atoms share a pair of electrons in order to"
"the central carbon 9. The C9-H sites of the fluorene ring are weakly acidic (pK = 22.6 in DMSO.) Deprotonation gives the stable fluorenyl ""anion"", nominally CH, which is aromatic and has an intense orange colour. The anion is a nucleophile, and most electrophiles react with it by adding to the 9-position. The purification of fluorene exploits its acidity and the low solubility of its sodium derivative in hydrocarbon solvents. Both protons can be removed from C9. For example, 9,9-fluorenyldipotassium can be obtained by treating fluorene with potassium metal in boiling dioxane. Fluorene and its derivatives can be deprotonated to"
"melting and boiling points of iodine are the highest among the halogens, conforming to the increasing trend down the group, since iodine has the largest electron cloud among them that is the most easily polarised, resulting in its molecules having the strongest van der Waals interactions among the halogens. Similarly, iodine is the least volatile of the halogens. Because it has the largest atomic radius among the halogens, iodine has the lowest first ionisation energy, lowest electron affinity, lowest electronegativity and lowest reactivity of the halogens. The interhalogen bond in diiodine is the weakest of all the halogens. As such,"
"Group 9 element Group 9, numbered by IUPAC nomenclature, is a group of chemical element in the periodic table. Members are cobalt (Co), rhodium (Rh), iridium (Ir) and perhaps also the chemically uncharacterized meitnerium (Mt). These are all transition metals in the d-block. All known isotopes of meitnerium are radioactive with short half-lives, and it is not known to occur in nature; only minute quantities have been synthesized in laboratories. Like other groups, the members of this family show patterns in electron configuration, especially in the outermost shells, resulting in trends in chemical behavior; however, rhodium deviates from the pattern."
"9,10-Dihydroanthracene 9,10-Dihydroanthracene is an organic compound that is derived from the polycyclic aromatic hydrocarbon anthracene. Several isomers of dihydroanthracene are known, but the 9,10 derivative is most common. It is a colourless solid that is used as a carrier of H in various chemical reactions. Because the aromaticity is not compromised for the flanking rings, anthracene is susceptible to hydrogenation at the 9- and 10- positions. It is produced in the laboratory by dissolving metal reduction using sodium/ethanol, an application of the Bouveault–Blanc reduction developed by Louis Bouveault and Gustave Louis Blanc in 1903. The reduction can be effected by"
"its explosive reaction with aluminium to form 2AlI. Astatine, the heaviest halogen, has only formed a few compounds, due to its radioactivity and short half-life, and no reports of a compound with an At–B, –Al, –Ga, –In, –Tl, or –Nh bond have been seen, although scientists think that it should form salts with metals. It has been noticed that the elements in the boron group have similar physical properties, although most of boron's are exceptional. For example, all of the elements in the boron group, except for boron itself, are soft. Moreover, all of the other elements in group 13"
"dehalogenation is a key reaction to convert toxic organohalides to less hazardous products. Among halogens, fluorine is the most electronegative atom and will have the highest tendency to make the strongest bond with carbon. The rate of dehalogenation depends on the bond strength between carbon and halogen atom. The bond dissociation energies of carbon-halogen bonds are described as: H3C-I (234 KJmol-1), H3C-Br (293 KJmol-1), H3C-Cl (351 KJmol-1), and H3C-F (452 KJmol-1). Thus, for the same structures the bond dissociation rate for dehalogenation will be: F« Cl Additionally, the rate of dehalogenation for alkyl halide also varies with steric environment and"
"each achieve a stable octet for themselves; at high temperatures, these diatomic molecules reversibly dissociate a pair of iodine atoms. Similarly, the iodide anion, I, is the strongest reducing agent among the stable halogens, being the most easily oxidised back to diatomic I. (Astatine goes further, being indeed unstable as At and readily oxidised to At or At, although the existence of At is not settled.) The halogens darken in colour as the group is descended: fluorine is a very pale yellow gas, chlorine is greenish-yellow, and bromine is a reddish-brown volatile liquid. Iodine conforms to the prevailing trend, being"
"very weak bonds within the diatomic F molecule.) This means, as you go down the periodic table, the reactivity of the element will decrease 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 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"
"most unreactive metals are listed last. Therefore, a metal higher on the list is able to displace anything on the list below it. The order of activity for metals, from most reactive to least reactive, is Li, K, Sr, Na, Ca, Mg, Al, Zn, Cr, Fe, Cd, Co, Ni, Sn, Pb, H, Sb, As, Bi, Cu, Hg, Ag, Pd, Pt, Au. Similarly, the halogens with the highest propensity to acquire electrons are the most reactive. The activity series for halogens, from highest to lowest, is F, Cl, Br, I. Due to the free state nature of A and B, all"
"Pentaborane(9) Pentaborane(9) is an inorganic compound with the formula BH. It is one of the most common boron hydride clusters, although it is a highly reactive compound. Because of its high reactivity toward oxygen, it was once evaluated as rocket or jet fuel. Like many of the smaller boron hydrides, pentaborane is colourless, diamagnetic, and volatile. It is related to pentaborane(11) (BH). Its structure is that of five atoms of boron arranged in a square pyramid. Each boron has a terminal hydride ligand and four hydrides span the edges of the base of the pyramid. It is classified as a"
"Within each group of nonmetals, reactivity decreases with each lower rows of the table (from a light element to a heavy element) in the periodic table, because the valence electrons are at progressively higher energies and thus progressively less tightly bound. In fact, oxygen (the lightest element in group 16) is the most reactive nonmetal after fluorine, even though it is not a halogen, because the valence shell of a halogen is at a higher principal quantum number. In these simple cases where the octet rule is obeyed, the valence of an atom equals the number of electrons gained, lost,"
"is a halogen atom bearing a negative charge. The halide anions are fluoride (F), chloride (Cl), bromide (Br), iodide (I) and astatide (At). Such ions are present in all ionic halide salts. Halide minerals contain halides. All these halides are colourless, high melting crystalline solids having high negative enthalpies of formation. Halide compounds such as KCl, KBr and KI can be tested with silver nitrate solution, AgNO. The halogen will react with Ag and form a precipitate, with varying colour depending on the halogen: For organic compounds containing halides, the Beilstein test is used. are used in high-intensity discharge lamps"
"by most acids: it is completely insoluble in nitric acid and dissolves slightly in aqua regia. Rhodium belongs to group 9 of the periodic table, but the configuration of electrons in the outermost shells is atypical for the group. This anomaly is also observed in the neighboring elements, niobium (41), ruthenium (44), and palladium (46). The common oxidation state of rhodium is +3, but oxidation states from +0 to +6 are also observed. Unlike ruthenium and osmium, rhodium forms no volatile oxygen compounds. The known stable oxides include , , , , and . Halogen compounds are known in nearly"
"Iodine Iodine is a chemical element with symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a lustrous, purple-black non-metallic solid at standard conditions that sublimes readily to form a violet gas. The elemental form was discovered by the French chemist Bernard Courtois in 1811. It was named two years later by Joseph Louis Gay-Lussac from this property, after the Greek ""ἰώδης"" ""violet-coloured"". Iodine occurs in many oxidation states, including iodide (I), iodate (), and the various periodate anions. It is the least abundant of the stable halogens, being the sixty-first most abundant element."
"few millikelvins. It is possible to produce exotic helium isotopes, which rapidly decay into other substances. The shortest-lived heavy helium isotope is helium-5 with a half-life of . Helium-6 decays by emitting a beta particle and has a half-life of 0.8 second. Helium-7 also emits a beta particle as well as a gamma ray. Helium-7 and helium-8 are created in certain nuclear reactions. Helium-6 and helium-8 are known to exhibit a nuclear halo. Helium has a valence of zero and is chemically unreactive under all normal conditions. It is an electrical insulator unless ionized. As with the other noble gases,"
"of the periodic table: Whereas all other group 8 elements have 2 electrons in the outermost shell, in ruthenium, the outermost shell has only one electron (the final electron is in a lower shell). This anomaly is observed in the neighboring metals niobium (41), molybdenum (42), and rhodium (45). Ruthenium has four crystal modifications and does not tarnish unless subject to high temperatures. Ruthenium dissolves in fused alkalis to give ruthenates (), is not attacked by acids (even aqua regia) but is attacked by halogens at high temperatures. Indeed, ruthenium is most readily attacked by oxidizing agents. Small amounts of"
"lithium and fluorine (appearing twice), or left floating above the other elements and not assigned to any group in the periodic table. Helium is almost always placed above neon (which is in the p-block) in the periodic table as a noble gas, although it is occasionally placed above beryllium due to their similar electron configuration. Hydrogen (H) is the chemical element with atomic number 1. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H. With an atomic mass of 1.00794 amu, hydrogen is the lightest element. Hydrogen is"
"additional electron is located in the aluminium cluster at the location directly opposite from the iodine atom. The cluster must therefore have a higher electron affinity for the electron than iodine and therefore the aluminium cluster is called a superhalogen (i.e., the vertical electron detachment energies of the moieties that make up the negative ions are larger than those of any halogen atom). The cluster component in the ion is similar to an iodide ion or a bromide ion. The related cluster is expected to behave chemically like the triiodide ion.<ref name=""bergeron/2005""></ref> Halogen The halogens () are a group in"
"halogens (fluorine, chlorine, bromine, iodine, and astatine). This state should be more stable than it is for thallium as the SO splitting of the 7p subshell is greater than that for the 6p subshell. Nihonium should be the most electronegative of the metallic group 13 elements, even more electronegative than tennessine, the period 7 congener of the halogens: in the compound NhTs, the negative charge is expected to be on the nihonium atom rather than the tennessine atom. The −1 oxidation should be more stable for nihonium than for tennessine. The electron affinity of nihonium is calculated to be around"
"Helium Helium (from ) is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas, the first in the noble gas group in the periodic table. Its boiling point is the lowest among all the elements. After hydrogen, helium is the second lightest and second most abundant element in the observable universe, being present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined. Its abundance is similar to this figure in the Sun and in Jupiter. This"
"compounds, as well as aromatic hydrocarbons such as benzene, toluene and limonene), whose study forms the core of organic chemistry. Alongside hydrogen, carbon can form compounds with the chemically similar halogens, forming haloalkanes. The simplest of this series, the halomethanes, contain compounds such as dichloromethane and iodoform. Other such important chemicals include vinyl chloride, which is used in the production of PVC. The other group 14 elements have a lower tendency to catenate. Silanes SiH are known for ""n"" = 1–8 (thermal stability decreasing as ""n"" increases), as are cyclosilanes SiH and SiH. They are very reactive, pyrophoric colourless gases"
"reactivity decreases as the atomic number increases. When a halogen combines with another element, the resulting compound is called a halide. One of the best examples of a halide is sodium chloride (NaCl). The d-block is on the middle of the periodic table and includes elements from columns 3 through 12. These elements are also known as the transition metals because they show a transitivity in their properties i.e. they show a trend in their properties in simple incomplete d orbitals. Transition basically means d orbital lies between s and p orbitals and shows a transition from properties of s"
"the hydrides have lower hardness and ductility than metal. Only a few percent of hydrogen can dissolve in zirconium. Excess hydrogen forms voids that weaken Zircalloy. Among Zircaloys, Zircaloy-4 is the least susceptible to hydrogen blistering. It is also used as a neutron moderator in thermal-spectrum nuclear reactors such as the TRIGA research reactor developed by General Atomics or the Soviet TOPAZ nuclear reactors. At neutron energies above 0.14 eV it is as effective at moderating a nuclear reactor as elemental hydrogen (the best known material), but far more dense, and therefore permits compact reactors with high power per unit"
"Hydrogen Hydrogen is a chemical element with symbol H and atomic number 1. With a standard atomic weight of , hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass. Non-remnant stars are mainly composed of hydrogen in the plasma state. The most common isotope of hydrogen, termed ""protium"" (name rarely used, symbol H), has one proton and no neutrons. The universal emergence of atomic hydrogen first occurred during the recombination epoch. At standard temperature and pressure, hydrogen is a colorless,"
"Rhodium, iridium, and meitnerium have no known biological roles. Group 9 element Group 9, numbered by IUPAC nomenclature, is a group of chemical element in the periodic table. Members are cobalt (Co), rhodium (Rh), iridium (Ir) and perhaps also the chemically uncharacterized meitnerium (Mt). These are all transition metals in the d-block. All known isotopes of meitnerium are radioactive with short half-lives, and it is not known to occur in nature; only minute quantities have been synthesized in laboratories. Like other groups, the members of this family show patterns in electron configuration, especially in the outermost shells, resulting in trends"
"atoms. If the number includes a fifth digit, the fifth number indicates the number of iodine atoms (though iodine in halon is rare). Any bonds not taken up by halogen atoms are then allocated to hydrogen atoms. For example, consider Halon 1211: C F Cl Br 1 2 1 1 Halon 1211 has one carbon atom, two fluorine atoms, one chlorine atom and one bromine atom. A single carbon only has four bonds, all of which are taken by the halogen atoms, so there is no hydrogen. Thus its formula is CF<nowiki>BrCl</nowiki>, and its IUPAC name is therefore bromochlorodifluoromethane. The"