The melting point and boiling point increase in turn (except poloniumMolecular crystal, so the melting and boiling points followrelative molecular massIncrease)
Oxygen group elementyesperiodic table of ele mentsGroup VI A elements on.This group includes oxygen (O), sulfur (S)selenium（Se）、tellurium（Te）、Polonium（Po）、鉝(Lv) Six elements, of which polonium is metal and tellurium isMetalloidOxygen, sulfur and selenium are typicalNonmetallic element。stayStandard statusThe elemental substances of other elements are solid except that oxygen is gas.On andmetallic elementWhen combining, the four elements of oxygen, sulfur, selenium and tellurium usually show - 2Oxidized state；But when sulfur, selenium and tellurium are in theirAcid radicalAt medium temperature, the highest oxidation state can reach+6.sometransition metalOftensulfideThe form of ore exists in the crust, such as FeStwo、ZnSEtc.
brief introduction
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Chalcogen
stayStandard statusThe elemental substances of other elements are solid except that oxygen is gas.In the compounds, oxygen, sulfur, selenium and tellurium usually show - 2Oxidized stateThe stability decreases from oxygen to tellurium;The highest oxidation state of sulfur, selenium and tellurium can reach+6.The simple substances of oxygen, sulfur and selenium can be directly combined with hydrogen to formhydride。[1]
In addition, oxygen group elements can also formOxygenateHowever, many properties are not similar to oxygen group elements.
·Atomic radiusWith the increase in sequence, the electronic capacity decreases in turn, and the oxidizability decreases in turn
Simple substance
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oxygen
oxygen
oxygenGeneral conditionsThe gas below is colorless, odorless and tasteless, with density of 1.429 g/l, 1.419 g/cm3 (liquid), 1.426 g/cm3 (solid), melting point of - 218.4 ℃, boiling point of - 182.962 ℃, and liquid formation at - 182.962 ℃Light blueLiquid, solidified to snowy light blue at - 218.4 ℃.Solids inValenceGenerally 0 and - 2.The ionization energy is 13.618Electron volt。exceptinert gasAll exceptchemical elementCan form compounds with oxygen.Most elements can be formed when heated in an oxygen containing atmosphereoxide。Many elements can form more than one oxide.Oxygen molecules can form at low temperatureshydrationcrystalO₂.H ₂ O and O ₂H ₂ O ₂, the latter is more unstable.Oxygen in airsolubilityYes: 4.89 ml/100 ml water (0 ℃) is the basis of life in water.Oxygen in the crustabundanceFirst place.The dry air contains 20.946% oxygen by volume;Water is composed of 88.81% oxygen by weight.In addition to O16, there are O17 and O18isotope。
It is usually a yellowish crystal, and its element name comes fromLatin, originally meant bright yellow.Several kinds of elemental sulfurAllotrope，Rhombic sulfur（Rhombic sulfur）AndMonoclinic sulfur[1]It is the most important crystalline sulfur known now.They are all made byS8annularMolecular composition.
Density Melting Point Boiling Point Existence Condition
sulfur Thermal conductivityandConductivityAll are poor.It is fragile and insoluble in water,Solubletocarbon disulfide(Elastic sulfurOnly partially dissolved).Amorphous sulfur is mainly elastic sulfur, which is obtained by rapidly pouring molten sulfur into ice water.Unstable, can be transformed into crystalline sulfur（Orthorhombic sulfur）, orthorhombic sulfur is the only stable sulfur at room temperatureExisting form。
The valence is - 2,+2,+4 and+6.First ionization energy 10.360Electron volt。The chemical property is relatively active, and can be compared with oxygen, metal, hydrogenhalogen(except bromine and iodine) and most known elements.Can also be compared with strongOxidizabilityAcid, salt, oxide, concentrated strong alkali solution reaction.It has positiveOxidized state, there is also negative oxidation state, which can formIonic compoundCovalentCompositeAnd coordinationCovalent compound。
selenium
selenium
scattered elementone of.In six known solidsAllotropeAmong them, three kinds of crystals (α monoclinic, β monoclinic, and gray triangular) are the most important.There are also threeAmorphous solidFormal existence;Two amorphous glassy forms, red and blackselenium。The former is brittle, with a density of 4.26g/cm3;The density of the latter is 4.28g/cm3.The first ionization energy is 9.752Electron volt。Selenium burns in the air and emits a blue flameSelenium dioxide（SeO₂）。It can also react directly with various metals and nonmetals, including hydrogen andhalogen。It cannot react with non oxidizing acid, but it is soluble inconcentrated sulfuric acid、nitric acidAnd strong alkali.Water-solubleHydrogen selenideCapable of precipitating many heavy metal ions into particlesSelenide[1]。Selenium andOxidized stateMetal with+1 can generate two typesSelenide, namely, positive selenide (M2Se) and acid selenide (MHSe).Positivealkali metalandalkaline-earth metalSelenideThe aqueous solution ofPolysulfidebe similar.
tellurium
There are crystalline and amorphousAllotrope。Ionization energy 9.009Electron volt。Crystalline tellurium has a silver white metallic appearance, with a density of 6.25 g/cm3, a melting point of 452 ℃, a boiling point of 1390 ℃, and a hardness of 2.5（Mohs hardness）。Insoluble in all solvents that do not react with it, its molecular weight at room temperature is still unknown.Amorphous tellurium (brown), density 6.00g/cm3, melting point 449.5 ± 0.3 ℃, boiling point 989.8 ± 3.8 ℃.Tellurium burns in air with a blue flame, generatingTellurium dioxide；AccessiblehalogenReaction, but not with sulfur and selenium.Soluble insulphuric acid, nitric acidPotassium hydroxideandPotassium cyanideSolution.Easy to conduct heat and electricity.
tellurium
Element source: telluriumscattered metals,SM One, there are twoAllotrope, one is crystalline and silvery whiteMetallic luster；The other is amorphous, which is black powder.Crystalline formtelluriumIts melting point is 449.8 ℃ and its density is 6.24g/cm3.It is brittle.Tellurium is similar to selenium in chemical properties and is generated by combustion in air or oxygenTellurium dioxide, emitting blue flame;Easy andhalogenTelluriumhalide, does not react with hydrogen at high temperatures.
The density is 9.4 g/cm3.The melting point is 254 ℃, and the boiling point is 962 ℃.All poloniumisotopeBothradioactivityOf.There are two known isotopic variants: α-PoIs a singlecube；β - Po is a single rhomboid.At about 36 ℃, α - Po transforms into β - Po.Metal, soft.physical propertyLike thallium, lead and bismuth.Chemical property approximationtellurium。Soluble in dilute mineral acid and dilutePotassium hydroxide。Polonium compounds are readily hydrolyzed and reduced.There are+2,+4 and+6 valence.PoloniumIt is the rarest element in the world.
The most common and easily available polonium isotope is210po , whichhalf lifeOnly 138 days, its radioactivity is nearly 5000 times greater than radium.Polonium-210 is very dangerous, and even a small amount of polonium-210 should be handled with great care.
chemical property
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Similarity
·It can react with most metals;
·Can be generated by combining with hydrogenationGaseous hydride；
·Can burn in oxygen;
·Maximum priceThe hydrate corresponding to the oxide is acid;
·Gaseous hydrideThe stability of β - lactamase gradually weakened;(from high temperature stable water to normal temperature decompositionHydrogen telluride）
·The basicity of the oxide gradually increases, and it begins to appear amphoteric (the 4-valent oxides of sulfur, selenium and tellurium are more and more acidic, while polonium dioxide is amphoteric)
chemical compound
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Common compounds of oxygen group elements include:oxide、sulfide、sulfate、SulfiteSelenate, tellurite.Some common compounds are listed below.
sulfur dioxide
sulfur dioxide(chemical formula: SO ₂) is the most common sulfuroxide。Colorless gas with strong pungent smell.One of the main atmospheric pollutants.Volcano eruptionThe gas will be ejected when, and sulfur dioxide will also be produced in many industrial processes.As coal and oil usually contain sulfur compounds, sulfur dioxide will be generated when burning.When sulfur dioxide is dissolved in water, it will formSulfite（acid rainThe main components of).If SO ₂ is further oxidized, it is usually found thatNitrogen dioxideWill generatesulphuric acid。
SO2 isAcid oxideIt has the common property of acid oxide.canWithThe aqueous solution of sulfur dioxide is obtained by water action, namely“Sulfite”（Intermediate acid）, but there is no sulfite molecule in the solution.SO2 reacts with alkali to formSulfiteandBisulfite。Withsodium hydroxideFor example, the product isNa2SO3NaHSO3 or NaHSO3 depends on their dosage relationship.Sulfur dioxide andAlkaline oxideThe reaction produces salt.
SO2 is also availableOxidizability, can react with reducing substances, such as: 2H2S+SO2==2H2O+3S.
SO2 is unstable in aqueous solution,Isolated air heating can occurDisproportionation reaction：3SO2+2H2O==2H2SO4+S
SO2 YesbleachIts bleaching effect is due to the formation of unstable colorless substances with some colored substances, but this colorless substance is easy to decompose to restore the original color of the substance, but this is only temporary, such as sulfur dioxide bleachingMagentaHeating restores color.In industry, sulfur dioxide is used to bleach paper. As a result, the paper will gradually turn yellow after being placed for a long time. This is because of the loss of sulfur dioxide.The bleaching of SO2 belongs to chemical change.
The relationship between SO2 solubility and temperature is shown in the following table:
22 g/100ml (0 °C)
15 g/100ml (10 °C)
11 g/100ml (20 °C)
9.4 g/100 ml (25 °C)
8 g/100ml (30 °C)
6.5 g/100ml (40 °C)
5 g/100ml (50 °C)
4 g/100ml (60 °C)
3.5 g/100ml (70 °C)
3.4 g/100ml (80 °C)
3.5 g/100ml (90 °C)
3.7 g/100ml (100 °C)
hydrogen sulfide
hydrogen sulfideIs a kind ofinorganic compound, chemical formula is H2S.Normally, it is a colorless, flammable acid gas with low concentrationTime bandIt smells like rotten eggs;When the concentration is high, there is no smell (because high concentration of hydrogen sulfide can paralyze the olfactory nerve).It is soluble in water. At 0 ° C, 1 volume of water can dissolve about 2.6 volumes of hydrogen sulfide.The aqueous solution of hydrogen sulfide is calledHydrosulfuric acidIt is a weak acid. When it is heated, hydrogen sulfide escapes from water.Hydrogen sulfide is an acute toxic substance. Inhaling a small amount of high concentration hydrogen sulfide can be fatal in a short time.Low concentration of hydrogen sulfideEye contact、respiratory systemandCentral nervous systemAll have an impact.
Hydrogen sulfide naturally exists in crude oil, natural gas, volcanic gas and hot springs.It can also be decomposed by bacteriaorganic compoundProduced in the process of.
Hydrogen sulfide is reducible, can occur with sulfur dioxide and other substancesRedox reaction。(See this entry → Compounds → Sulfur dioxide).
Laboratory production of hydrogen sulfide: FeS+2HCl=FeCl2+ H2S↑；In addition, hydrogen sulfide can also pass through some sulfides (such asAluminium sulfide）Hydrolysis of: 6H2O+Al2S3= 3H2S↑ + 2Al(OH)3.
Sulfur trioxide
Sulfur trioxideIt is an oxide of sulfur, with the molecular formula of SO3.Its gaseous form is a serious pollutant and one of the main sources of acid rain.Sulfur trioxideMedium, sulfurousOxidation numberIs+6, and the numerator isNonpolar molecule。Sulfur trioxideIts melting point is very low, only 16.9 ℃, and its boiling point is only 45 ℃.
sulphuric acid(Sulfuric acid), molecular formula H2SO4, is a colorless viscous high density strong corrosive liquid.It is an important chemical raw material, also known asMother of Chemical Industry, is also a common chemical reagent.Sulfuric acid is extremely corrosive, so you should be very careful when using it.
The melting point of sulfuric acid is 10 ℃, the boiling point is 290 ℃, and waterMiscibility。Sulfuric acid dissolves in water and emits strong heat, so pay attention to "acid" when diluting sulfuric acidWater ingress”。
concentrated sulfuric acidyesDehydration, such as dropping concentrated sulfuric acid onsucroseThe white sugar gradually turns black and releases white gas（Water vaporEvaporated into air and then condensedwaterBeads):C12H22O11→ 12 C + 11 H2O 。Concentrated sulfuric acidWater absorptionIt can strongly absorb water and release heat.(If water molecules are absorbed, it is water absorption, such as absorptionCopper sulfate pentahydrateFive molecules of water.)
concentrated sulfuric acidAcidic and oxidizingIts oxidizability is generally reflected in the case of heating.concentrated sulfuric acidOxidation productNot hydrogen,It'ssulfur dioxide, sulfur, hydrogen sulfide or metalsulfide(andreducing agentQuantity and type).Concentrated sulfuric acid can oxidize metals, for example, concentrated sulfuric acid can oxidize simple copper: Cu+2 H2SO4 → CuSO4+SO2+2 H2O（side reactionWith 5Cu+4H2SO4 →Cu2S+3CuSO4+4H2O, etc.);Concentrated sulfuric acid can also oxidize nonmetals such as phosphorus, sulfur, selenium, carbon, etc., as well as redox hydrides such as hydrogen sulfide,Hydrogen iodideandHydrogen bromide(In case of excess reducing agent, concentrated sulfuric acid can be reduced to sulfur, hydrogen sulfide and sulfur dioxide respectively).
Dilute sulfuric acidReact with active metals to release hydrogen, such aszincAnd sulfuric acidzinc sulfateAnd hydrogen (Zn+H2SO4==ZnSO4+H2 ↑), this reaction is used to produce hydrogen in the laboratory.In individual casesSulfate radicalCan be reduced: 4Mn+5H2SO4==H2S ↑+4MnSO4+4H2O.Sulfuric acid can alsometallic oxideReaction: CuO+H2SO4==CuSO4+H2Ocopper sulphateThe method ofCupric oxideEnvironmental protection).Sulfuric acid can react with certain salts:BaCl2+H2SO4==BaSO4↓+2HCl。The acidity of sulfuric acid can makeLitmusThe solution turns red.
Sulfur hexafluoride is produced by the combination of simple substances, and the reaction will also generate other sulfurfluorideasDisulfide decafluoride, which can be disproportionated by heating, and thensodium hydroxideProcess to remove the remainingSulfur tetrafluorideAnd purification.Sulfur hexafluoride is an extremely inert gas, which does not mix with waterhydrochloric acid、sodium hydroxideAnd molten sodium, but will interact with metallithiumReact and release heat.
InhalationSulfur hexafluorideThe sound becomes thicker, because the weight of sulfur hexafluoride gas reduces the speed of sound waves in human vocal cords by half, which is the opposite of the sound becoming thinner after inhaling helium.
Disulfide dichloride
Disulfide dichloride(S2Cl2) is a yellow red liquid with irritating and suffocating odor, which is strong in the airFuming。It decomposes into sulfur when encountering watersulfur dioxide、Hydrogen chloride。Soluble in ether, benzenecarbon disulfide。It is stable at room temperature, decomposes into corresponding simple substances at 100 ° C, and completely decomposes at 300 ° C.Dichlorodisulfide can be reduced tochlorideandsulfide。AndchlorineReaction formationSulfur dichloride。Energy and metaloxideorsulfideThe reaction produces metal chlorides.
Sulfuryl chloride molecule is distortedtetrahedronStructure, sulfur is+6Oxidized stateThe S-O bond contains some double bond components.On catalysts such asActivated carbon、Ferric chlorideorcamphorIn the presence of,sulfur dioxideAndchlorineThionyl chloride is generated by combination and purified by distillation.Reaction formula: SO2+Cl2 → SO2Cl2.Chlorosulfonic acidThe heating can also obtain the sulfuryl chloride: 2ClSO3H → SO2Cl2+H2SO4.
Sulfuryl chloride will start to decompose above 100 ° C to obtain sulfur dioxide and chlorine, which will make the reagent yellow.Decomposition also occurs when placed for a long time.
Sulfoxide chloride
Sulfoxide chloride, also known as thionyl chloride, is ainorganic compound, chemical formula isSOCl2。At normal temperature and pressure, it is a colorless and distillable liquid, which will decompose at 140 ° C.Sometimes, SOCl2 is easily confused with sulfuryl chloride (SO2Cl2), but their chemical properties are very different.The molecular configuration of thionyl chloride is conical, in which the sulfur (VI) center contains a pair ofLone pair electron。andphosgeneIt is a planar configuration.
Because sulfoxide chloride reacts strongly with water, SOCl2 will not exist in nature.
Sulfoxide chloride is a colorless or light yellow fuming liquid with strong irritating smell.It decomposes into sulfur dioxide and hydrogen chloride when encountering water or alcohol.yesOrganic moleculeSelective hydroxyl groups inSubstitutive action。The substance is soluble in benzenechloroform、carbon disulfideandcarbon tetrachloride。Heat to 150 ° C to start decomposition, and decompose completely at 500 ° C.
copper sulphate, chemical formula CuSO4, white powder, its common form is its crystal, copper sulfate pentahydrate (CuSO4 · 5H2O), a blue solid.Its aqueous solution is due tohydrationCopper ionBecause of its blue color, anhydrous copper sulfate is often used to test the existence of water in the laboratory.In real production and life, copper sulfate is often used for refiningRefined copper, andHydrated limeMixed preparable pesticidesBordeaux liquid。Copper sulfate is a heavy metal salt,Toxic, adultLethal dose0.9g/kg。In case of ingestion, a large amount of milkegg-whiteEtcproteinFood, or use EDTA calcium sodium salt for detoxification.Purpose:
Sterilizing agent: Copper sulfate can be used to kill fungi.AndLimewaterGenerate after mixingBordeaux liquid, used to control lemonsGrapeSuch as fungi on crops.dilute solutionbe used foraquariumSterilization and removalsnail。Since copper ion is toxic to fish, the dosage must be strictly controlled.Most fungi can be killed with very low concentration of copper sulfate.In addition, copper sulfate can also be used to controlEscherichia coli。
Copper sulfate can be used for inspectionanemia。Drop the blood sampleCopper sulfate solutionMedium, if the blood sample contains enoughhemoglobin, the blood sample will sink rapidly;ifhemoglobinIf the content is not enough, the blood sample will be suspended in the solution.
Organic synthesis:Copper sulfate can be used in organic synthesis.Anhydrous salt for catalytic conversionAcetal reaction。Five water salt andpotassium permanganateThe reaction produces an oxidant forPrimary alcoholConversion of.
Chemistry teaching:Copper sulfate can be used forcrystalGeneration test andElectroplated copperexperiment.Copper sulfate is also commonly used for demonstrationExothermic reaction, the presentation willMagnesium stripInsert into copper sulfate solution.Copper sulfate can also be used to demonstrate crystalswater lossThe process of weathering and obtaining crystal water.In the middle school textbook, there is an experiment to replace copper with iron. It is to insert iron bars (or iron wires) into copper sulfate solution to replace red copper.
Selenium dioxide
Selenium dioxide(chemical formula: SeO2) isselenium(4) Ofoxide, colorless crystal, is the most commonly used selenium compound, sublimated at 315 ℃, toxic, and the body will emit a special odor after ingestion (should be taken after ingestionvitamin C）。Selenium burns in air (blue flame)nitric acid、hydrogen peroxideReactive oxidation, orSeleniteSelenium dioxide can be obtained by dehydration.Selenium dioxide is soluble in water and generatesSelenite；Dissolve in alkali to form selenite.It is an oxidant in organic synthesis and can be used for allylic oxidation, Riley oxidation reaction, etc.cyclohexanone React to get 1,2-Cyclohexanedione，TrioxaneReaction resultsGlyoxal。
Hydrogen selenide
Hydrogen selenideIt is a kind of extremely toxic, odorous, colorless gas, which is more acidic than hydrogen sulfide and can be gradually decomposed by heating and burning.Flammable.Usually made of metalSelenideAnd water or dilute acid.
Other selenium compounds
SeleniteIt's seleniumOxyacidOf which seleniumOxidized stateIs+4.It is whiteOrthorhombic systemCrystal, PolarSolubleIn water, bySelenium dioxideDissolve in a small amount of water slowlyEvaporative crystallizationCombined usePotassium hydroxideObtained by drying.The slightly distorted SeO3 groups in the crystal are connected by strong hydrogen bonds.Solid selenite decomposes at 150 ℃.In stronger oxidants (such as ozonechlorine、PermanganateSelenite can also be oxidized toSelenic acid。Selenite is highly toxic, and poisoning symptoms may be delayed for several hours, including coma, nauseahypotension, which may cause death in serious cases.
Selenic acidIt is one of the oxygen containing acids of selenium, in which the valence of seleniumOxidized stateAt the same concentration, the oxidation is far stronger than sulfuric acid, and gold can be dissolved.
Hydrogen tellurideIt is a colorless, foul smelling, extremely toxic, colorless gas that is unstable, decomposed by heating, has strong reducibility, and can be oxidized by some common oxidants.
primaryTelluric acidIt is soluble in water and hot waterWhite crystal, chemical formula H6TeO6, is very weakdiprotic acid[2]（Ionization constantK1=2.09X10 ^ - 8,K2=6.46X10^-12），Usually only 2hydrogen atomWill be replaced, but in some cases, all six hydrogen atoms can be replaced.Raw telluric acid is decomposed by heatingTellurium trioxide。Prototelluric acid isweak acid。Prototelluric acid is highly oxidizing and can dissolve silver, andConcentrated hydrochloric acidOfMixed acid(Free Cl2 exists) can dissolve platinum and gold, and itself is reduced toTellurium dioxide。SO2 orN2H4The original telluric acid can be reduced to elemental tellurium.
