The starrkingschool.netistry the Oxygen The starrkingschool.netistry the Ozone Oxygen as an Oxidizing certified dealer
Peroxides Methods of preparing O2 The starrkingschool.netistry of Sulfur
The result of distinctions in the strength of X-X and also X=X Bonds The impact of distinctions in the Electronegativities that Sulfur and also Oxygen The result of distinctions in the abilities of Sulfur and also Oxygen to increase Their Valence covering

The starrkingschool.netistry ofOxygen

Oxygen is the most abundant element on this planet. Theearth"s crust is 46.6% oxygen by weight, the oceans are 86%oxygen by weight, and also the atmosphere is 21% oxygen through volume. Thename oxygen originates from the Greek trunk oxys,"acid," and gennan, "to kind orgenerate." Thus, oxygen literally way "acidformer." This surname was presented by Lavoisier, who noticedthat compounds rich in oxygen, such as SO2 and P4O10,dissolve in water to give acids.

The electron configuration of an oxygen atom 2s22p4 says that neutral oxygen atom canachieve one octet of valence electron by sharing two pairs ofelectrons to kind an O=O twin bond, as displayed in the figurebelow.


According come this Lewis structure, every one of the electrons in theO2 molecule room paired. The compound need to thereforebe diamagnetic it need to be repelled through amagnetic field. Experimentally, O2 is found to it is in paramagneticit isattracted come a magnetic field. This deserve to be explained by assumingthat there room two unpaired electrons in the

* antibondingmolecular orbitals the the O2 molecule.

This photograph shows the the liquid O2 is so strong attracted come a magnetic ar that it will certainly bridge the gap between the poles that a horseshoe magnet.

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At temperatures listed below -183oC, O2condenses to form a liquid v a characteristic irradiate blue colorthat results from the absorption of light with a wavelength of630 nm. This absorb is not checked out in the gas phase and isrelatively weak even in the liquid because it requires that threebodies 2 O2 molecules and also a photon collidesimultaneously, i m sorry is a really rare phenomenon, also in theliquid phase.

The starrkingschool.netistry ofOzone

The O2 molecule is no the just elemental kind ofoxygen. In the existence of lightning or another source of aspark, O2 molecules dissociate to type oxygen atoms.

O2(g) " width="17" height="9"> 2 O(g)

These O atoms deserve to react through O2 molecules to formozone, O3,

O2(g) + O(g) " width="17" height="9"> O3(g)

whose Lewis structure is displayed in the figurebelow.


Oxygen (O2) and ozone (O3) are examplesof allotropes (from the Greek definition "inanother manner"). By definition, allotropes are differentforms of an element. Due to the fact that they have different structures,allotropes have different starrkingschool.netical and physical properties (seetable below).

Properties of allotropes of Oxygen

Oxygen (O2 ) Ozone (O3 )
Melting allude -218.75oC -192.5oC
Boiling Point -182.96oC -110.5oC
Density (at 20oC) 1.331 g/L 1.998 g/L
O-O bond order 2 1.5
O-O shortcut length 0.1207 nm 0.1278 nm

Ozone is an rough compound v a sharp, pungent smell thatslowly decomposes come oxygen.

3 O3(g) " width="17" height="9"> 3 O2(g)

At low concentrations, ozone deserve to be relatively pleasant. (Thecharacteristic clean odor linked with summer thunderstorms isdue come the development of little amounts the O3.)

Exposure to O3 at higher concentrations leader tocoughing, rapid beating the the heart, chest pain, and generalbody pain. In ~ concentrations above 1 ppm, ozone is toxic.

One that the characteristic properties of ozone is the abilityto absorb radiation in the ultraviolet portion of the spectrum (> 300 nm), thereby offering a filter that protects united state fromexposure to high-energy ultraviolet radiation emitted by the sun.We deserve to understand the prominence of this filter if us think aboutwhat happens when radiation native the sun is absorbed by our skin.

Electromagnetic radiation in the infrared, visible, andlow-energy sections of the ultraviolet spectrum ( 3 and also CF2Cl2,which had actually been provided as refrigerants and also as propellants in aerosolcans, were start to accumulate in the atmosphere. In thestratosphere, at altitudes that 10 come 50 km over the earth"ssurface, chlorofluorocarbons decompose to type Cl atom andchlorine oxides such together ClO when they absorb sunlight. Cl atomsand ClO molecules have an odd number of electrons, as shown inthe number below.


As a result, this substances are unusually reactive. In theatmosphere, castle react through ozone or v the oxygen atoms thatare necessary to kind ozone.

Cl + O3 " width="17" height="9"> ClO + O2
ClO + O " width="17" height="9"> Cl + O2

Molina and also Rowland postulated that these building material wouldeventually diminish the ozone shield in the stratosphere, withdangerous effects for organic systems that would beexposed to boosted levels of high-energy ultraviolet radiation.

Oxygen as anOxidizing agent

Fluorine is the only element that is much more electronegative thanoxygen. Together a result, oxygen gains electron in virtually all itsstarrkingschool.netical reactions. Every O2 molecule must acquire fourelectrons to satisfy the octets that the 2 oxygen atoms withoutsharing electrons, as displayed in the number below.


Oxygen because of this oxidizes steels to type salts in i m sorry theoxygen atoms room formally current as O2- ions. Rustforms, for example, once iron reacts with oxygen in the presenceof water to provide a salt that formally has the Fe3+and O2- ions, with an typical of 3 water moleculescoordinated to each Fe3+ ions in this solid.

4 Fe(s) + 3 O2(g) " width="17" height="9"> 2 Fe2O3(s) 3 H2O

Oxygen additionally oxidizes nonmetals, such as carbon, to formcovalent compounds in i m sorry the oxygen formally has an oxidationnumber that -2.

C(s) + O2(g) " width="17" height="9"> CO2(g)

Oxygen is the perfect example of an oxidizing agentbecause it increases the oxidation state of nearly any substancewith which the reacts. In the course of that is reactions, oxygen isreduced. The substances that reacts through are because of this reducingagents.


It takes four electrons to reduce an O2 molecule toa pair of O2- ions. If the reaction stops after the O2molecule has obtained only two electrons, the O22-ion presented in the figure listed below is produced.


This ion has actually two an ext electrons 보다 a neutral O2molecule, which means that the oxygen atoms have to share just asingle pair of bonding electron to attain an octet the valenceelectrons. The O22- ion is dubbed the peroxideion due to the fact that compounds that contain this ion room unusually wealthy inoxygen. They room not just oxides they room (hy-)peroxides.

The easiest means to prepare a peroxide is come react salt orbarium steel with oxygen.

2 Na(s) + O2(g) " width="17" height="9"> Na2O2(s)
Ba(s) + O2(g) " width="17" height="9"> BaO2(s)

When these peroxides are allowed to react with a solid acid,hydrogen peroxide (H2O2) is produced.

BaO2(s) + 2 H+(aq) " width="17" height="9"> Ba2+(aq) + H2O2(aq)

The Lewis structure of hydrogen peroxide contains an O-Osingle bond, as shown in the number below.


The VSEPR concept predicts that the geometry roughly each oxygenatom in H2O2 should be bent. But thistheory can not predict even if it is the 4 atoms need to lie in thesame aircraft or even if it is the molecule need to be visualized as lyingin two intersecting planes. The experimentally determinedstructure that H2O2 is shown in the figurebelow.


The H-O-O bond edge in this molecule is just slightly largerthan the angle in between a pair of nearby 2p atomicorbitals on the oxygen atom, and the angle in between the planesthat type the molecule is slightly bigger than the tetrahedralangle.

The oxidation variety of the oxygen atoms in hydrogen peroxideis -1. H2O2 can therefore act together anoxidizing agent and capture two an ext electrons to form a pair ofhydroxide ions, in i beg your pardon the oxygen has actually an oxidation number of-2.

H2O2 + 2 e- " width="17" height="9"> 2 OH-

Or, it have the right to act as a to reduce agent and lose a pair ofelectrons to form an O2 molecule.

H2O2 " width="17" height="9"> O2 + 2 H+ + 2 e-

Reactions in i beg your pardon a compound simultaneously undergoes bothoxidation and reduction are called disproportionationreactions. The products of the disproportionation that H2O2are oxygen and water.

2 H2O2(aq) " width="17" height="9"> O2(g) + 2 H2O(l)

The disproportionation the H2O2 is anexothermic reaction.

2 H2O2(aq) " width="17" height="9"> O2(g) + 2 H2O(l)
o = -94.6 kJ/mol H2O

This reaction is reasonably slow, however, in the absence of acatalyst, such together dust or a metal surface. The principal offers ofH2O2 revolve approximately its oxidizing ability.It is used in dilute (3%) solutions as a disinfectant. In moreconcentrated solutions (30%), it is used as a bleaching agent forhair, fur, leather, or the lumber pulp offered to do paper. In veryconcentrated solutions, H2O2 has actually been usedas rocket fuel because of the ease through which that decomposes togive O2.

Methods ofPreparing O2

Small quantities of O2 gas have the right to be all set in anumber of ways.

1. By decomposing a dilute solution of hydrogen peroxide withdust or a steel surface together the catalyst.

2 H2O2(aq) " width="17" height="9"> O2(g) + 2 H2O(l)

2. By reaction hydrogen peroxide with a solid oxidizingagent, such as the permanganate ion, MnO4-.

5 H2O2(aq) + 2 MnO4-(aq) + 6 H+(aq) " width="17" height="9"> 2 Mn2+(aq) + 5 O2(g) + 8 H2O(l)

3. By pass an electric existing through water.

2 H2O(l) " width="17" height="9"> 2 H2(g) + O2(g)

4. By heater potassium chlorate (KClO3) in thepresence that a catalyst until it decomposes.

2 KClO3(s) " width="17" height="9"> 2 KCl(s) + 3 O2(g)

The starrkingschool.netistry ofSulfur

Because sulfur is directly listed below oxygen in the periodic table,these facets have similar electron configurations. As a result,sulfur forms numerous compounds that space analogs that oxygen compounds,as presented in the table below. Instances in this table show how theprefix thio- deserve to be supplied to suggest compounds in whichsulfur replace instead replace an oxygen atom. The thiocyanate (SCN-)ion, for instance, is the sulfur-containing analog the the cyanate(OCN-) ion.

Oxygen Compounds and also Their Sulfur Analogs

Oxygen Compounds Sulfur Compounds
Na2O (sodium oxide) Na2S (sodium sulfide)
H2O (water) H2S (hydrogen sulfide)
O3 (ozone) SO2 (sulfur dioxide)
CO2 (carbon dioxide) CS2 (carbon disulfide)
OCN- (cyanate) SCN- (thiocyanate)
OC(NH2)2 (urea) SC(NH2)2 (thiourea)

There are 4 principal differences in between the starrkingschool.netistry ofsulfur and oxygen.

1. O=O dual bonds are lot stronger than S=S double bonds.

2. S-S solitary bonds are virtually twice as solid as O-O singlebonds.

3. Sulfur (EN = 2.58) is much less electronegativethan oxygen (EN = 3.44).

4. Sulfur can expand its valence shell to hold an ext than eightelectrons, yet oxygen cannot.

These seemingly minor differences have necessary consequencesfor the starrkingschool.netistry of this elements.

The effect ofDifferences in the stamin of X-X and X=X Bonds

The radius that a sulfur atom is around 60% bigger than the ofan oxygen atom.


As a result, that is harder for sulfur atoms to come closeenough together to kind bonds. S=S dual bonds room thereforemuch weaker than O=O double bonds.

Double bonds between sulfur and also oxygen or carbon atoms can befound in compounds such as SO2 and CS2 (seefigure below). However these double bonds are much weaker than theequivalent double bonds come oxygen atom in O3 or CO2.The shortcut dissociation enthalpy for a C=S double bond is 477kJ/mol, for example, vice versa, the bond dissociation enthalpy because that aC=O double bond is 745 kJ/mol.


Elemental oxygen is composed of O2 molecule in whicheach atom completes the octet the valence electron by sharing twopairs that electrons v a solitary neighboring atom. Due to the fact that sulfurdoes not form strong S=S double bonds, elemental sulfur usuallyconsists the cyclic S8 molecule in which every atomcompletes that is octet through forming single bonds to two neighboringatoms, as presented in the figure below.


S8 molecules deserve to pack to kind more than onecrystal. The most stable form of sulfur is composed of orthorhombiccrystals that S8 molecules, which are often uncovered nearvolcanoes. If these crystals room heated until they melt and also themolten sulfur is climate cooled, an allotrop of sulfur consistingof monoclinic crystals of S8 molecule isformed. These monoclinic crystals gradually transform themselvesinto the much more stable orthorhombic structure over a duration oftime.

The tendency of an element to kind bonds to itself is dubbed catenation(from the Latin catena, "chain"). Becausesulfur creates unusually solid S-S single bonds, that is better atcatenation than any type of element except carbon. Together a result, theorthorhombic and monoclinic creates of sulfur room not the onlyallotropes that the element. Allotropes of sulfur also exist thatdiffer in the size of the molecule that form the crystal. Cyclicmolecules the contain 6, 7, 8, 10, and 12 sulfur atom areknown.

Sulfur melts at 119.25oC to kind a yellow liquidthat is less viscous than water. If this liquid is heated come 159oC,it turns into a dark red liquid the cannot it is in poured native itscontainer. The viscosity of this dark red fluid is 2000 timesgreater than that of molten sulfur due to the fact that the cyclic S8molecules open up up and link together to form long chains of asmany as 100,000 sulfur atoms.


16 K(s) + S8(s) " width="17" height="9"> 8 K2S(s)

This is no the just product that deserve to be obtained, however. Avariety of polysulfide ions through a charge of -2 have the right to be producedthat differ in the number of sulfur atom in the chain.


The effect ofDifferences in the Electronegativities that Sulfur and Oxygen

Because sulfur is much less electronegative 보다 oxygen, that ismore likely to form compounds in i m sorry it has actually a positiveoxidation number (see table below).

Common Oxidation Numbers for Sulfur

Oxidation Number Examples
-2 Na2S, H2S
-1 Na2S2, H2S2
0 S8
+1 S2Cl2
+2 S2O32-
+21/2 S4O62-
+3 S2O42-
+4 SF4, SO2, H2SO3, SO32-
+5 S2O62-
+6 SF6, SO3, H2SO4, SO42-

In theory, sulfur deserve to react through oxygen to form either SO2or SO3, whose Lewis structures are provided in the figurebelow.


In practice, combustion of sulfur compounds provides SO2,regardless of whether sulfur or a compound of sulfur is burned.

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S8(s) + 8 O2(g) " width="17" height="9"> 8 SO2(g)
CS2(l) + 3 O2(g) " width="17" height="9"> CO2(g) + 2 SO2(g)
3 FeS2(s) + 8 O2(g) " width="17" height="9"> Fe3O4(s) + 6 SO2(g)

Although the SO2 created in these reactions shouldreact with O2 to form SO3, the rate of thisreaction is very slow. The rate of the conversion of SO2into SO3 have the right to be greatly increased by adding anappropriate catalyst.

2 SO2(g) " width="17" height="9"> 2 SO3(g)

Enormous amounts of SO2 are created by industryeach year and also then converted to SO3, which deserve to be usedto create sulfuric acid, H2SO4. In theory,sulfuric acid have the right to be make by dissolve SO3 gas inwater.

SO3(g) + H2O(l) " width="17" height="9"> H2SO4(aq)

In practice, this is not convenient. Instead, SO3is absorbed in 98% H2SO4, whereby it reactswith the water to kind additional H2SO4molecules. Water is climate added, as needed, to save theconcentration that this solution in between 96% and also 98% H2SO4by weight.

Sulfuric acid is by much the most crucial industrialstarrkingschool.netical. That has even been argued that over there is a directrelationship between the amount of sulfuric acid a countryconsumes and also its conventional of living. An ext than 50% that thesulfuric acid created each year is used to make fertilizers. Therest is provided to do paper, fabricated fibers and also textiles,insecticides, detergents, feeding additives, dyes, drugs,antifreeze, paints and also enamels, linoleum, fabricated rubber,printing inks, cellophane, photographic film, explosives,automobile batteries, and metals such as magnesium, aluminum,iron, and also steel.

Sulfuric acid dissociates in water to provide the HSO4-ion, i m sorry is known as the hydrogen sulfate, or bisulfate, ion.

A range of salts deserve to be formed by instead of the H+ions in sulfuric acid through positively charged ions, such together theNa+ or K+ ions.

Sulfurous mountain doesn"t dissociate in water come as great extentas sulfuric acid, however it is still feasible to replace the H+ions in H2SO3 with optimistic ions to formsalts.

Sulfuric acid and also sulfurous acid room both examples of a classof compounds known as oxyacids, due to the fact that they areliterally acids the contain oxygen. Since they space negativeions (or anions) the contain oxygen, the SO32-and SO42- ion are known as oxyanions.The Lewis frameworks of few of the oxides of sulfur that formoxyacids or oxyanions are offered in the table below.

One of these oxyanions deserves unique mention. This ion,which is recognized as the thiosulfate ion, is created by the reactionbetween sulfur and the sulfite (SO32-) ion.

The effect ofDifferences in the abilities of Sulfur and also Oxygen to broaden TheirValence covering

The electron configuration of oxygen and also sulfur room usuallywritten together follows.

Although this notation shows the similarity between theconfigurations the the 2 elements, the hides one importantdifference that enables sulfur to increase its valence covering to holdmore than eight electrons.

Oxygen reacts v fluorine to form OF2.

The reaction stop at this point because oxygen can hold onlyeight electron in its valence shell, as shown in the figurebelow.


Sulfur reacts with fluorine to form SF4 and SF6,shown in the number below, since sulfur can expand its valenceshell to hold 10 or even 12 electrons.

S8(s) + 16 F2(g) " width="17" height="9"> 8 SF4(g)
S8(s) + 24 F2(g) " width="17" height="9"> 8 SF6(g)