The noble gases are the nonmetal, inert elements in group 18 (previously known as group 0) of the periodic table. In Chemistry a group, also known as a family, is a vertical column in the Periodic table of the Chemical elements There are 18 groups in In the Periodic table of the elements, a period is a horizontal row of the table A period 1 element is one of the Chemical elements in the first row (or period) of the periodic table of the chemical elements. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical A period 2 element is one of the Chemical elements in the second row (or period) of the periodic table of the chemical elements. Neon (ˈniːɒn is the Chemical element that has the symbol Ne and Atomic number 10 A period 3 element is one of the Chemical elements in the third row (or period) of the periodic table of the elements. This article pertains to the chemical element For other uses see Argon (disambiguation. A period 4 element is one of the Chemical elements in the fourth row (or period) of the periodic table of the elements. Krypton (ˈkrɪptən or /ˈkrɪptɒn/ from kryptos "hidden" is a Chemical element with the symbol Kr and Atomic number 36 A period 5 element is one of the Chemical elements in the fifth row (or period) of the periodic table of the elements. Xenon (ˈzɛnɒn or) is a Chemical element represented by the symbol Xe. A period 6 element is one of the Chemical elements in the sixth row (or period) of the periodic table of the elements, including the Lanthanides Radon (ˈreɪdɒn is the Chemical element that has the symbol Rn and Atomic number 86 A period 7 element is one of the Chemical elements in the seventh row (or period) of the periodic table of the elements. Ununoctium (ˌjuːnəˈnɒktiəm or /ˌʌnəˈnɒktiəm/ also known as eka-radon or element 118, is the temporary IUPAC name for Nonmetal is a term used in Chemistry when classifying the Chemical elements On the basis of their general physical and chemical properties every element in the In English to be inert is to be in a state of doing little or nothing A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. The periodic table of the chemical elements is a tabular method of displaying the Chemical elements Although precursors to this table exist its invention is Chemically, they are very stable because they have the maximum number of valence electrons their outer shell can hold, causing them to rarely react with other elements. In chemistry valence electrons are the Electrons contained in the outermost or valence, Electron shell of an Atom. An electron shell may be crudely thought of as an Orbit followed by Electrons around an Atom nucleus. Under normal conditions, they are odorless, colorless, monatomic gases. In Physics and Chemistry, monatomic is a combination of the words "mono" and "atomic" and means "single Atom. This page is about the physical properties of gas as a state of matter The melting and boiling points for each noble gas are close together; consequently, only a small temperature range exists for each to be in a liquid state. Liquid is one of the principal States of matter. A liquid is a Fluid that has the particles loose and can freely form a distinct surface at the boundaries of

The five noble gases that have stable isotopes are helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe). Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical Neon (ˈniːɒn is the Chemical element that has the symbol Ne and Atomic number 10 This article pertains to the chemical element For other uses see Argon (disambiguation. Krypton (ˈkrɪptən or /ˈkrɪptɒn/ from kryptos "hidden" is a Chemical element with the symbol Kr and Atomic number 36 Xenon (ˈzɛnɒn or) is a Chemical element represented by the symbol Xe. They have several important applications in industries such as lighting, welding, and space exploration. There is also one naturally-occuring radioactive noble gas, radon (Rn), which to its radioactivity, has been studied much less than the previous five members of the group. Radon (ˈreɪdɒn is the Chemical element that has the symbol Rn and Atomic number 86 Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. A synthetic member of the group ununoctium (Uuo) has been discovered, but very little is known of its properties due to its extremely limited availability. In chemistry the Chemical elements labeled as synthetic are too unstable to be found naturally on Earth. Ununoctium (ˌjuːnəˈnɒktiəm or /ˌʌnəˈnɒktiəm/ also known as eka-radon or element 118, is the temporary IUPAC name for Another synthetic element, ununquadium (Uuq), may turn out to have similar chemical and physical characteristics as other noble gases, and therefore may be a "noble gas" without being a member of group 18. Ununquadium (ˌjuːnənˈkwɒdiəm or /ˌʌnənˈkwɒdiəm/ is the temporary name of a radioactive Chemical element in the Periodic table that has the

History and etymologies

"Noble gas" is translated from the German word Edelgas first used in 1898 by Hugo Erdmann^[1] to refer to the extremely low level of reactivity that most of the elements in Group 18 exhibit under normal conditions. Hugo Erdmann ( 8 May 1862 &ndash 25 June 1910) was the German chemist who discovered together with his doctoral advisor Jacob Volhard The noble gases have also been referred to as "inert gases", but this is an inaccurate label because several of them participate in chemical reactions. "Inert gases" is also used in a narrower sense for Noble gases An inert gas is any Gas that is not reactive with elements ^[2] Another term that is seldom used is "rare gases",^[3] but this is also inaccurate because argon forms a fairly considerable part (0. This article pertains to the chemical element For other uses see Argon (disambiguation. 94% by volume, 1. 3% by mass) of the Earth's atmosphere. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five ^[4]

Helium was first detected in the Sun due to its characteristic spectral lines. A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range compared

Pierre Janssen and Joseph Norman Lockyer, were the first to discover a noble gas in 1868 while looking at the chromosphere of the Sun, and named it helium after the Greek name of the Sun, ἥλιος (Helios). Pierre Jules César Janssen ( February 22, 1824 &ndash December 23, 1907) was a French astronomer who along with the English Sir Joseph Norman Lockyer, FRS ( May 17, 1836 &ndash August 16, 1920) was an English scientist and astronomer The chromosphere (literally "colour sphere" is a thin layer of the Sun 's atmosphere just above the Photosphere, roughly 10000 kilometres deep The Sun (Sol is the Star at the center of the Solar System. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical In Greek mythology the Sun was personified as Helios (ˈhiliˌɑs ( Ἥλιος Latinized as Helius) ^[5][6] Before them, in 1784, the English chemist and physicist Henry Cavendish had discovered that air contains a small proportion of a substance that was less reactive than nitrogen. Henry Cavendish, FRS (10 October 1731 - 24 February 1810 was a British Scientist noted for his discovery of Hydrogen or what he called "inflammable Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 ^[7] A century later, in 1895, Lord Rayleigh discovered that some samples of nitrogen from the air were a different density than nitrogen that resulted from chemical reactions. John William Strutt 3rd Baron Rayleigh OM (12 November 1842 &ndash 30 June 1919 was an English Physicist who with William Ramsay, discovered A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called Along with scientist William Ramsay, Lord Rayleigh theorized that the nitrogen extracted from air was associated with another gas, leading to an experiment that successfully isolated a new element, argon, for the Greek αργό(ν) (inactive). Sir William Ramsay (2 October 1852 &ndash 23 July 1916 was a Scottish chemist who discovered the Noble gases and received the Nobel Prize in This article pertains to the chemical element For other uses see Argon (disambiguation. ^[7] With this discovery, they realized that an entire class of gases was missing from the periodic table. This page is about the physical properties of gas as a state of matter In 1895, in his search for argon, Ramsay also managed to isolate helium for the first time, while heating the mineral clevite. Cleveite is a radioactive Mineral containing Uranium and found in Norway. In 1902, having accepted the evidence for elements helium and argon, Mendeleev placed these Noble Gases in Group 0 in his arrangement of the elements. Dmitri Ivanovich Mendeleev (sometimes spelled Mendeleyev; Дми́трий Ива́нович Менделе́ев) ( &ndash) was a Russian chemist and ^[8]

Ramsay continued to search for these gases using the method of fractional distillation to separate liquid air into several components, and in 1898 discovered the elements krypton, neon, and xenon, and named them after the Greek κρυπτός (kryptos, hidden), νέος (neos, new), and ξένος (xenos, stranger). Fractional distillation is the separation of a mixture into its component parts or fractions such as in separating Chemical compounds by their Boiling point by heating Liquid Air was the brand name of an unusual Automobile produced by a joint American / English concern between 1899 and 1902 Krypton (ˈkrɪptən or /ˈkrɪptɒn/ from kryptos "hidden" is a Chemical element with the symbol Kr and Atomic number 36 Neon (ˈniːɒn is the Chemical element that has the symbol Ne and Atomic number 10 Xenon (ˈzɛnɒn or) is a Chemical element represented by the symbol Xe. Radon was first identified in 1898 by Friedrich Ernst Dorn,^[9] and was named as radium emanation, but was not considered a noble gas until 1904, when its characteristics were similar to other noble gases. Radon (ˈreɪdɒn is the Chemical element that has the symbol Rn and Atomic number 86 Friedrich Ernst Dorn ( 27 July 1848 &ndash 16 December 1916) was a German Physicist who was the first to discover that Radium (ˈreɪdiəm is a radioactive Chemical element which has the symbol Ra and Atomic number 88 ^[10]

The discovery of the noble gases helped to develop general understanding of atomic structure. In 1895, French chemist Henri Moissan attempted to form a reaction between fluorine and argon, one of the noble gases, but this failed. Ferdinand Frederick Henri Moissan ( September 28, 1852 &ndash February 20, 1907) was a French Chemist who won the Fluorine, fluorum meaning "to flow" is the Chemical element with the symbol F and Atomic number 9 Scientists were unable to prepare chemical compounds of argon until the early 20th century, although these attempts still helped to develop new theories of atomic structure. Learning from these experiments, Danish physicist Niels Bohr proposed in 1913 that the electrons in atoms are arranged in shells surrounding the nucleus, and that for all noble gases except for helium, the outermost shell always contains eight electrons. Niels Henrik David Bohr (nels ˈb̥oɐ̯ˀ in Danish 7 October 1885 – 18 November 1962 was a Danish Physicist who made fundamental contributions to understanding The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J An electron shell may be crudely thought of as an Orbit followed by Electrons around an Atom nucleus. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom In 1916, research concluded that an octet of electrons in the outer shell was the most stable arrangement for any atom, causing them to be unreactive with any other element because they did not require any more electrons to complete the outer shell. ^[10]

It was not until 1962 when Neil Bartlett discovered the first true chemical compound of a noble gas, xenon hexafluoroplatinate (Xe⁺[PtF₆]⁻). For the playwright see Neil Bartlett. Neil Bartlett was a chemist best known for his discovery of Noble gas compounds He taught Xenon hexafluoroplatinate is the description of the product obtained from the combination of Platinum hexafluoride and Xenon in an experiment that proved the chemical ^[11] Soon, the first compounds of other noble gases were discovered: in 1962 for radon, radon fluoride,^[12] and in 1963 for krypton, krypton difluoride (KrF₂). Radon difluoride ( is a compound of Radon, a Noble gas. Radon reacts readily with Fluorine to form a solid compound but this decomposes on attempted vaporization See also Krypton fluoride laser Krypton difluoride, KrF2 was the first compound of Krypton discovered ^[13] The first stable compound of argon was reported in 2000, when argon fluorohydride (HArF) was characterized at very low temperatures (40 Kelvins). Argon fluorohydride (HArF is the first known compound of the Chemical element Argon. The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic ^[14]

In December 1998, scientists at the Joint Institute for Nuclear Research working in Dubna, Russia, bombarded plutonium (Pu) with calcium (Ca) to produce a single atom of element 114,^[15] temporarily named ununquadium (Uuq). The Joint Institute for Nuclear Research, JINR (Объединённый институт ядерных исследований ОИЯИ in Dubna, Moscow Oblast Dubna (Дубна́ is a town in Moscow Oblast, Russia. Being under immediate jurisdiction of Moscow Oblast it is situated on the territory of Taldomsky Russia (Россия Rossiya) or the Russian Federation ( Rossiyskaya Federatsiya) is a transcontinental Country extending Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 Ununquadium (ˌjuːnənˈkwɒdiəm or /ˌʌnənˈkwɒdiəm/ is the temporary name of a radioactive Chemical element in the Periodic table that has the ^[16] First chemistry experiments indicate that this element may be the first superheavy element to show abnormal noble-gas-like properties. In Chemistry, transuranium elements (also known as transuranic elements) are the Chemical elements with Atomic numbers greater than 92 (the atomic ^[17] Another discovery was made in October 2006 when scientists from the Joint Institute for Nuclear Research and Lawrence Livermore National Laboratory successfully obtained ununoctium (Uuo) by bombarding californium (Cf) with calcium (Ca),^[18] a synthetically created element in Group 18. The Lawrence Livermore National Laboratory ( LLNL) in Livermore California is a scientific research laboratory founded by the University of California in 1952 Ununoctium (ˌjuːnəˈnɒktiəm or /ˌʌnəˈnɒktiəm/ also known as eka-radon or element 118, is the temporary IUPAC name for Californium (ˌkælɪˈforniəm is a Metallic Chemical element with the symbol Cf and Atomic number 98 Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 ^[19] There is currently no practical use for the element because it is very unstable. ^[20]

Chemical properties

Neon, like all noble gases except helium, has a "full" (eight electron) valence (outermost) electron shell.

The noble gases make up Group 18 of the periodic table. The periodic table of the chemical elements is a tabular method of displaying the Chemical elements Although precursors to this table exist its invention is The confirmed members are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical Neon (ˈniːɒn is the Chemical element that has the symbol Ne and Atomic number 10 This article pertains to the chemical element For other uses see Argon (disambiguation. Krypton (ˈkrɪptən or /ˈkrɪptɒn/ from kryptos "hidden" is a Chemical element with the symbol Kr and Atomic number 36 Xenon (ˈzɛnɒn or) is a Chemical element represented by the symbol Xe. Radon (ˈreɪdɒn is the Chemical element that has the symbol Rn and Atomic number 86 ^[21] All these noble gases are colorless, odorless, tasteless, and nonflammable under normal conditions. They were once labeled Group 0 in the periodic table because it was believed that they had a valence of zero, so their atoms could not combine with those of other elements to form chemical compounds. History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. However, it was later discovered that some of them do indeed form compounds, causing this label to fall into disuse. ^[10] Very little is known about the properties of the last member, ununoctium (Uuo). Ununoctium (ˌjuːnəˈnɒktiəm or /ˌʌnəˈnɒktiəm/ also known as eka-radon or element 118, is the temporary IUPAC name for

All of the noble gases have full valence electron shells. An electron shell may be crudely thought of as an Orbit followed by Electrons around an Atom nucleus. In Atomic physics and Quantum chemistry, electron configuration is the arrangement of Electrons in an Atom, Molecule, or other ^[22] Valence electrons are the outermost electrons of an atom and are normally the only electrons that participate in chemical bonding. In chemistry valence electrons are the Electrons contained in the outermost or valence, Electron shell of an Atom. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic Atoms with full valence electron shells are extremely stable and therefore do not tend to form chemical bonds. A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic However, heavier noble gases such as radon are held less firmly together by electromagnetic force than lighter noble gases such as helium, making it easier to remove outer electrons from heavy noble gases. In Physics, the electromagnetic force is the force that the Electromagnetic field exerts on electrically charged particles In 1962, an experiment successfully removed electrons from xenon, a noble gas, by the chemical process of oxidation. Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state ^[10]

As a result of this closed shell, the noble gases can be used in conjunction with the electron configuration notation to form the "noble gas notation". In Atomic physics and Quantum chemistry, electron configuration is the arrangement of Electrons in an Atom, Molecule, or other To do this, the nearest noble gas that precedes the element in question is written first, and then the electron configuration is continued from that point forward. For example, the electron notation of carbon is 1s²2s² 2p², and the noble gas notation is [He] 2s²2p². Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 This notation makes it easier to identify elements, and is shorter and easier than writing out the full notation of atomic orbitals. An atomic orbital is a Mathematical function that describes the wave-like behavior of an electron in an atom ^[23]

Compounds

Main article: Noble gas compound

Structure of XeF₄, one of the first noble gas compounds to be discovered. Noble gas compounds are Chemical compounds that include an element from Group 18 Noble gas

The noble gases exhibit extremely low chemical reactivity, and only a few hundred noble gas compounds have been characterized. Noble gas compounds are Chemical compounds that include an element from Group 18 Noble gas ^[24] No true chemical compounds of helium or neon have yet been formed, while xenon, krypton, and argon have shown some reactivity in the laboratory. A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. Lack of reactivity among the noble gases is caused by a full valence shell, resulting in little tendency to gain or lose electrons. ^[25] The noble gases have very weak interatomic force, and consequently they have very low melting and boiling points. In Physics, Chemistry, and Biology, intermolecular forces are forces that act between stable Molecules or between functional groups of The melting point of a solid is the temperature range at which it changes state from solid to Liquid. The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid All of them are monatomic gases under standard conditions, including the elements with larger atomic masses than many normally solid elements. In Physics and Chemistry, monatomic is a combination of the words "mono" and "atomic" and means "single Atom. This page is about the physical properties of gas as a state of matter In Physical sciences standard conditions for temperature and pressure are Standard sets of conditions for experimental measurements to allow comparisons to be made The atomic mass (ma is the Mass of an atom most often expressed in unified atomic mass units The atomic mass may be considered to be the total mass ^[10]

In 1933, Linus Pauling predicted that the heavier noble gases would be able to form compounds with fluorine and oxygen. Linus Carl Pauling (February 28 1901 – August 19 1994 was an American Scientist, Peace activist, Author and educator. Fluorine, fluorum meaning "to flow" is the Chemical element with the symbol F and Atomic number 9 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Specifically, he predicted the existence of krypton hexafluoride and xenon hexafluoride (XeF₆), speculated that XeF₈ might exist as an unstable compound, and suggested that xenic acid would form perxenate salts. Xenon hexafluoride is the Chemical compound with the formula XeF6 Xenon (ˈzɛnɒn or) is a Chemical element represented by the symbol Xe. Fluorine, fluorum meaning "to flow" is the Chemical element with the symbol F and Atomic number 9 Xenic acid is a Noble gas compound formed by the dissolution of Xenon trioxide in Water. The perxenates are salts of Perxenic acid, H 4 Xe[[oxygen O]]6 ^[26][27] These predictions proved quite accurate, except that XeF₈ is now predicted to be not only thermodynamically unstable, but kinematically unstable,^[28] and as of 2006 has not been made.

Xenon compounds are the most numerous of the noble gas compounds that have been characterized. ^[24][29][30] Most of them have the xenon atom in the oxidation state of +2, +4, +6, or +8 bonded to an electronegative atom of fluorine or oxygen, such as in xenon difluoride (XeF₂), xenon tetrafluoride (XeF₄), xenon hexafluoride (XeF₆), xenon tetroxide (XeO₄), and sodium perxenate (Na₄XeO₆). In Chemistry, the oxidation state is an indicator of the degree of Oxidation of an Atom in a Chemical compound. Fluorine, fluorum meaning "to flow" is the Chemical element with the symbol F and Atomic number 9 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Xenon difluoride is a powerful Fluorinating agent, with the chemical formula, is one of the most stable Xenon compounds. Xenon tetrafluoride, Xe[[Fluorine F4]] is one of the chemical compounds derived from the Noble gas xenon Xenon hexafluoride is the Chemical compound with the formula XeF6 Xenon tetroxide (molecular formula XeO4) is a yellow Crystalline Solid that is stable below −35 Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22 The perxenates are salts of Perxenic acid, H 4 Xe[[oxygen O]]6 Some of these compounds have found practical application as oxidizing agents. An oxidizing agent or oxidising agent (also called an oxidant, oxidizer or oxidiser) can be defined as either a Chemical compound As of 2007, close to a hundred compounds of xenon bonded to other elements, such as organoxenon compounds (those bonded to hydrogen or carbon), or those bonded to nitrogen, or chlorine, or even to xenon itself, or even gold or mercury. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and Gold (ˈɡoʊld is a Chemical element with the symbol Au (from its Latin name aurum) and Atomic number 79 Mercury (ˈmɜrkjʊri also called quicksilver or hydrargyrum, is a Chemical element with the symbol Hg ( Latinized hydrargyrum ^[24][31]

In theory, radon is more reactive than xenon, and therefore should form chemical bonds much easier than xenon does. In practice though, due to the high radioactivity of the radon isotopes, only a few fluorides and oxides have been characterized. There are thirty four known Isotopes of Radon ( Rn) The most stable isotope is 222Rn which is a Decay product (daughter product of Fluoride is the reduced form of Fluorine. Both organic and Inorganic compounds containing the element fluorine are considered fluorides An oxide is a Chemical compound containing at least one Oxygen atom as well as at least one other element ^[32] Krypton on the other hand is less reactive than xenon, but quite a few compounds of it have been reported with krypton in the oxydation state of +2, inluding some bonded to nitrogen and oxygen (but only stable under −60 °C and −90 °C respectively). ^[24] No compounds of helium, or neon, are known and as of 2007 HArF is still the only confirmed compound of argon. Argon fluorohydride (HArF is the first known compound of the Chemical element Argon. ^[24]

An endohedral fullerene compound containing a noble gas.

In addition to the compounds where a noble gas atom is involved in a covalent bond, noble gases also form non-covalent compounds. The first to be discovered were the clathrates, where a noble gas atom is trapped within cavities of crystal lattices of certain organic and inorganic substances. A clathrate or clathrate compound or cage compound is a Chemical substance consisting of a lattice of one type of molecule trapping The essential condition for their formation is that the guest (noble gas) atoms should be of appropriate size to fit in the cavities of the host crystal lattice. For instance, Ar, Kr and Xe can form clathrates with hydroquinone, but He and Ne cannot fit because they are too small. Hydroquinone, also benzene-14-diol or quinol, is an Aromatic Organic compound which is a type of phenol, having the Chemical

Noble gases can form endohedral fullerene compounds where the noble gas atom is trapped inside a fullerene molecule. "C60" and "C-60" redirect here For other uses see C60 (disambiguation. In 1993, it was discovered that when C₆₀ is exposed to noble gases at high pressure, complexes such as He@C₆₀ can be formed (the "@" notation means that He is contained inside C₆₀ but not covalently bound to it). ^[33] Endohedral complexes with He, Ne, Ar, Kr, and Xe have been obtained. ^[34] These compounds have found use in the study of the structure and reactivity of fullerenes by means of the nuclear magnetic resonance of the noble gas atom.

Bonding

Noble gas compounds such as XeF₂ are said to be hypervalent because they violate the octet rule. A hypervalent molecule is a Molecule that contains one or more typical elements ( group 1 2 13-18 formally bearing more than eight Electrons in their The octet rule is a simple chemical Rule of thumb that states that Atoms tend to combine in such a way that they each have eight Electrons in Bonding in such compounds can be explained using a 3-center-4-electron bond model. The 3-center-4-electron bond is a model used to explain bonding in Hypervalent molecules such as Phosphorus pentafluoride, Sulfur hexafluoride, the ^[35][36] This model, first proposed in 1951,^[37] considers bonding of three colinear atoms; for example, bonding in XeF₂ is described by a set of three molecular orbitals (MOs) derived from p-orbitals on each atom. In Chemistry, a molecular orbital (or MO) is a region in which an Electron may be found in a Molecule. Bonding results from the combination of a filled p orbital from Xe with one half-filled p orbital from each F atom, resulting in a filled bonding orbital, a filled non-bonding orbital, and an empty antibonding orbital. Antibonding (or anti-bonding) is a type of chemical bonding. An antibonding orbital is a form of Molecular orbital (MO that is located outside the region The HOMO is localized on the two terminal atoms. HOMO and LUMO are Acronyms for highest occupied Molecular orbital and lowest unoccupied Molecular orbital, respectively This localization of charge is accommodated by the fact that the fluorine atoms are highly electronegative. " Electronegativity " is the opposite of " Electropositivity," which describes an element's ability to donate electrons

Bonding in XeF₂ according to the 3-center-4-electron bond model.

Bonding in XeF₂ can also be represented using the resonant Lewis structures shown below:

In this representation, the octet rule is not broken, the bond orders are 1/2, and there is increased electron density in the fluorine atoms. Resonance in Chemistry is a theory used to represent and model certain types of non-classical Molecular structures Resonance is a key component Lewis structures, also called Lewis-dot diagrams are diagrams that show the bonding between Atoms of a Bond order is the number of bonds between a pair of atoms For example in Nitrogen N≡N the bond order is 3 in Acetylene H−C≡C−H the bond order between the These is consistent with the molecular orbital picture discussed above.

Physical properties

Noble gases have several unique qualities when compared with other elements. For example, the boiling and freezing points of helium are lower than those of any other known substance. Helium is also the only element that cannot be solidified by cooling in normal conditions. A pressure of 25 standard atmospheres (2,500 kPa) must be applied at a temperature of 1 K (−272. The Standard atmosphere is an international reference pressure defined as 101325 Pa and formerly used as unit of Pressure (symbol atm The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic 15 °C/−457. The Celsius Temperature scale was previously known as the centigrade scale. 87 °F) to convert it to a solid. Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686–1736 a German Physicist who proposed it in 1724 Argon is the most plentiful noble gas on Earth, while krypton is the lightest noble gas to be converted into chemical compounds. Xenon is the least volatile of the noble gases obtainable from the air, and although it is an unusually safe anesthetic, its compounds are toxic. Radon is formed from radioactive gas along with helium as radium decays. It takes several days for radon to decay, forming helium and heavy metals, typically lead. Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly ^[10]

Applications

Liquid helium is used to cool the superconducting magnets in modern MRI scanners.

The abundance of the noble gases in the universe decrease as their atomic number increases; helium is the most common element in the universe after hydrogen. See also List of elements by atomic number In Chemistry and Physics, the atomic number (also known as the proton The Universe is defined as everything that Physically Exists: the entirety of Space and Time, all forms of Matter, Energy All of the noble gases are present in the Earth's atmosphere, so they are obtained primarily from air using the methods of liquefaction of gases and fractional distillation, with the exception of helium and radon. Liquefaction of gases includes a number of phases used to convert a Gas into a Liquid state Fractional distillation is the separation of a mixture into its component parts or fractions such as in separating Chemical compounds by their Boiling point by heating Helium is typically produced from oil wells, and radon is usually isolated from the radioactive decomposition of dissolved radium compounds. West Texas PumpjackJPG|thumb|right|300px|This Pumpjack located south of Midland TX is a common sight in West Texas. Radium (ˈreɪdiəm is a radioactive Chemical element which has the symbol Ra and Atomic number 88 ^[10]

Noble gases have very low boiling and melting points, making them useful as cryogenic refrigerants. Cryogenics is often used incorrectly to refer to Cryonics, cryopreserving humans or animals A refrigerant is a compound used in a heat cycle that undergoes a Phase change from a Gas to a Liquid and back In particular, liquid helium, which boils at 4 K, is widely used in superconducting magnets such as those used in MRI and NMR. Helium exists in Liquid form only at very low Temperatures The Boiling point and critical point depend on the Isotope A superconducting magnet is an Electromagnet that is built using superconducting coils

Helium has a low solubility in fluids, leading to its use, along with oxygen, for breathing by deep-sea divers because helium does not dissolve in blood and therefore does not form bubbles upon decompression. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Nitrogen was used before helium; since it formed bubbles upon decompression, it lead to a condition known as decompression sickness, or "the bends". Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Decompression sickness (DCS, the diver’s disease, the bends, caisson disease is the name given to a variety of symptoms suffered by a person ^[10]

In the early 20th century, hydrogen was used as a lifting gas for lighter-than-air aircraft. However, as the LZ 129 Hindenburg disaster demonstrated when the hydrogen in the envelope engulfed the airship in flames,^[40] its combustibility was a dangerous characteristic and resulted in hydrogen being replaced with helium in blimps and balloons because of its lightness and incombustibility, despite its decrease in buoyancy. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Terminology In some countries airships are also known as dirigibles from the French (fr ''diriger'' to direct plus -ible) meaning "directable" A balloon is a flexible bag filled with a type of Gas, such as Helium, Hydrogen, Nitrous oxide or air. ^[10]

Noble gases are commonly used in lighting because of their lack of chemical reactivity. Lighting includes both artificial Light sources such as lamps and natural illumination of interiors from Daylight. Argon is often used inside incandescent light bulbs because it is inert, and it is also used in the synthesis of air- and moisture-sensitive compounds as an alternative to nitrogen. This article pertains to the chemical element For other uses see Argon (disambiguation. The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric Light that works by Incandescence, (a general Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Some of the noble gases glow distinctive colors when used inside lighting tubes, such as neon lights, which produce an orange-red color. Neon signs are luminous-tube signs that contain neon or other inert gases at a low pressure Helium and argon are commonly used to shield welding arcs and the surrounding base metal from the atmosphere during welding. Arc welding uses a Welding power supply to create an Electric arc between an electrode and the base material to melt the metals at the welding point In Chemistry, the term base metal is used informally to refer to a Metal that oxidizes or corrodes relatively easily and reacts variably with ^[10] Krypton is used in lasers by doctors performing eye surgery. Krypton (ˈkrɪptən or /ˈkrɪptɒn/ from kryptos "hidden" is a Chemical element with the symbol Kr and Atomic number 36 A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. Eye surgery, also known as orogolomistician surgery or ocular surgery, is Surgery performed on the Eye or its Adnexa, typically by ^[41] Xenon is commonly used in xenon arc lamps, and it is also used as an anaesthetic because it is nonflammable and readily eliminated from the body. Xenon (ˈzɛnɒn or) is a Chemical element represented by the symbol Xe. A xenon arc lamp is an artificial light source Powered by Electricity, it uses Ionized Xenon gas to produce a bright white light that closely Anesthesia, or anaesthesia (see spelling differences; from Greek grc αν- an-, "without" and grc αἲσθησις Because radon is highly radioactive, its only uses have been those that exploit this property, such as radiotherapy. Radiation therapy (or radiotherapy) is the medical use of Ionizing radiation as part of Cancer treatment to control Malignant ^[10]

Colors produced by the different noble gases when used in neon tubes

Helium

Neon

Argon

Krypton

Xenon

See also

• Noble metal

Notes

References

• Bobrow (2007-12-05), CliffsAP Chemistry, CliffsNotes, ISBN 047013500X, <http://www.amazon.com/dp/047013500X> . Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 63 BC - Cicero reads the last of his Catiline Orations. CliffsNotes (formerly Cliffs Notes and often incorrectly CliffNotes are a series of Student Study guides available primarily in the United States.
• Ozima, Minoru (2002), Noble Gas Geochemistry, Cambridge University Press, ISBN 0521803667, <http://books.google.com/books?id=CBM2LJDvRtgC> . Cambridge University Press (known colloquially as CUP is a Publisher given a Royal Charter by Henry VIII in 1534