Chemical Bonding PDF

UNIT -IV Chapter 1.. CHEMICAL BONDING Weightage of Marks = 09, Teaching Hours = 06 Syllabus 1.1 IndianChemistry:Philosophyof atom by Acharya Kanad. 1.2 El...

UNIT -IV Chapter 1.. CHEMICAL BONDING Weightage of Marks = 09, Teaching Hours = 06 Syllabus 1.1 IndianChemistry:Philosophyof atom by Acharya Kanad. 1.2 Electronic Theory of Valency:Assumptions,Chemical Bonds:Types and characteristics of electrovalentbond, Covalent bond, Coordinate bond, Hydrogen bond, Metallic bond and Intermolecular forcesof attraction. 1.3 Molecular Arrangement inSolids, Liquids and Gases. 1.4 Structureof Solids: Crystalline and amorphous solids, Properties - of metolicsolids Unitcellof Simplecubic,Body centered cubic,Face centeredcubic, Hexagonal - closepack crystals. SpecificObjectives Explain the properties ofgivenmaterial based on bond formation. Describethe molecularstructureofgivensolids, liquidsand gases. Describethe crystalstructureof givensolids. Explain propertíes of metallicsolid. INTROD 1.1.1 Philosophyof an Atom AncientIndianand Greek philosophers consideredmatter to be discontinuousand composed of extremelysmalland invisible particles. Firsttime in the world the philosophy of an atom was discussed by Acharya Kanada, originally known by the name of Kashyap. He was born around 600 BC to 800 BC in Prabhas Kshetra near Dwaraka in present day Gujarat,India.He was the son of a philosophernamed Ulka. U|G),also Kanda (sanskrit: known as Uluka,Kashyapa,Kanabhaksha,Kanabhujwas an ancientIndiannaturescientist and philosopherwho founded the VaisheshikaSchoolof IndianPhilosophy. e MaharshiKanada has postulatedthatifwe go on dividingmatter,we willget the smaler and smaller of a matter.If particles we continue withdividingmatterultimately a stage will come when we willcome acrossthe smallestparticle of matterwhich cannot be divided further.He calledthese smallestparticles as parman. Today we calledthese particlesas atoms. Thistheory occurredto him whilehe was walkingwithfood inhishand.As he nibbledatthe food in hishand,throwingaway the smallparticlesone by one until he was unableto break itdown anymore and it lefta smell on hishands. He realizedthathe could not dividethe (1.1) BasicScence :Chemistry(Sem. I) 1.2 ChemicalBonding foodintofurtherpartsand the realizationof a matter which cannot be dividedfurtherCarmo intoexistence.Maharshi Kanad explainedthe atomic theory of matter.To explainhisthery he appliedlogicand realism.Accordingto him thistheory isas given below: 1. Matter consistsof indestructible particles calledparamanus.Param means ultimateand anu means particle. 2. Everythingcan be partitioned. 3. Paramanus does notexistinfreestate. 4. Paramanus combines with otherparamanusto form a biggerparticles called molecules 5. Paramanus are indivisible and itcan not be furtherdivided,because itisa state at which no measurement can be attributed. 6. Paramanus areinfinitesimal particles. 7. Atom is a minute object invisible to the naked eye which come into being in at an instant; which isindestructible and hence eternal. 8. Atoms may combine invarious ways to produce chemicalchanges in presenceof other factorslikeheat. Forexample, blackeningof earthenpot or ripeningof fruit. 9. Paramanuor atom can have two states- stateof motion and stateof absoluterest. Kanada's atom was - 700 times bigger than what we know today,conceptualizing such small sizes 2,500 years back without the aid of modern scientific instruments is a remarkablefeat. Acharya Kanad estimated atom as size of 7 x10 meter.Then same theorywas discovered by John Dalton(1766 to 1844). John Dalton,an English School Master, gave hisfamous atomic theoryin 1808 regardingthe structure of matterto explainthe laws of chemicalcombination. Main pointsof Dalton's atomictheory areas given below: All mattersaremade of atoms. Atoms areindivisible and indestructible. atoms of a given element areidentical All in mass and properties. Atoms of differentelements aredissimilar in mass and properties. Compounds areformed by a combination oftwo or more different kindsof atoms. chemicalreactionisa rearrangement of atoms. A -1.2Typesof ChemicalBond Except noble gases, atoms of activeelements do not have free existence.They readily combine to form molecules. Moleculesareformed by certainkindof chemicalbonds between similar or dissimilar atoms. Number of atoms in a molecule isthe atomicity of thatmoleculeor compound. Atomicity Monoatomic Diatomic Triatomic (onlyone atom inthe (two atoms in the (threeatoms inthe molecule)e.g.Inertgases molecule) molecule) and metallic atoms e.g.H2, Cl2, Nz, O, etc. e.g. O3, H0,CO, Atoms of activeelements are not stablein free state but the chemicalbonds make them stable. A chemicalbond isthe force of attraction between the atoms to hold them together as a stablemolecule.  : BasicSclence Chemlstry(Sem. I) 1.3 Chemical Bonding. Examples : +Chemicalbonds H,0 molecule O, molecule oto +Chemical bonds There are differenttypes of chemical bonds (primarybonds),as ionic bond/covalent bond/co0-ordinate bond/metallic bond existing between atoms of molecules. Some secondary bonds (generally weak) also existeither within the same molecule or between the neighbouring molecules known as Van der Waal's force of attraction and hydrogen bond. Itshould be noted thatchemicalpropertiesof compounds mainlydepend upon the strength of primary bonds (ionic/covalent/co-ordinate/metallic) in the molecule and physical propertiesincluding mechanicalstrength depend upon secondary bonds (Van der Waal's forceof attraction,/hydrogen bond). 1.1.3 Electronic Theoryof Valency The salient featuresof the electronic theory ofvalencyare : (i)The electrons presentin the outermost orbitof an atom of an elenment determinethe valencyof an elementand hence called'valencyelectrons'. (i)Atoms of a elements with 8 electronsinthe outermostorbitorshellor2 electrons, ifthere isone orbitor shell only (K shell) are stable. Therefore, electronic arrangementinwhich 8 electrons(octet)or 2 electrons(duplet)are present in the outermost shellof an atom is known as stableconfiguration. (i) Only those atoms of the elements havinglessthan 8 electrons intheiroutermost shellare capableof chemicalcombination(such elements areactiveor unstableelements),so that they may alsoacquirea stableinertgas configuration with 8 electrons(duplet, ifone shell only)in the outermostshell. (iv) Octet (orduplet)can be achievedeither(a)by the transfer (gainor loss) of one or more electrons from the atom of one element to the atom ofanotherelement (b)by the sharing of electrons between the atoms. (v) Number of electronsdonated or accepted or shared by atom of an element in orderto completeitsoctet ordupletiscalleda valency. (vi) Accordingtotheirmode offormation, as: typesof bonds may be classified different (1)Ionicbond (orelectrovalent bond). (2)Covalentbond. (3)Coordinatebond. bond. (4)Metallic In addition, therecan be attractive interactions, known by the name hydrogen bond and Van der Waals interactions. 1.1.4 ChemicalBond Formation In chemical bond formation, by losing, atoms interact gainingor sharingof electrons so as to acquirenearestinertgas configuration. Therefore,there are followingmodes of chemicalcombinationsby which a chemicalbond is formed between two combiningatoms. (1) By transfer ofelectrons(lose orgain) forms ionicor electrovalent bond. (2)By mutualsharingof electrons formscovalent bond. (3)By one sidedsharingof electrons forms co-ordinate bond.  1.4 Chemical Bonding BasloSclence:Chemistry(Sem. l) bond. through of electrons metal lattice forms metallic (4)By delocallzation two electronegativeatoms bridge between (5)When hydrogen atom acts as a foorms hydrogen bond. bond : 1.IonicorElectrovalent of one or more electronsfromthe completetransfer the outermost An lonicbond is formed atom, so that both acquirestable by outermost shellof another dissimilar shell of one atom to inertgas configuration. becomes a positive: acquires positivecharge and The atom which loses the electrons, (cation). acquiresnegative charae which gains electrons, On the other hand, the other atom becomes a negativeion (anion). electrocts. and anion)combine together,due to (cation These two oppositelycharged ions or ioniccompound. to form an electrovalent forcesof attraction, between the positiveion (cation) a bond is the force of attraction Thus, electrovalent negativeion (anion). a. by means of an electron Chemical reactions between two combining atoms are represented atomns of combiningelements are represented diagram or atomicdiagram in which the electronsas dot placed aroundthe symbol. symbols of that element and the valence MgCl;etc. Examples of electrovalent compounds areNaF,KCI, MgS, CaO,AlCl3, character and electronegative of elements Table 1.1: Tableshowing electropositive Nature Elements Electronic Valency Valency configuration electron 11Na 2,8, 1 1 + 1 Metallic : Loses electronswith ease to 2 +2 form electropositiveradicals (except 12Mg 2, 8, 2 +3 He, H2). 2, 8, 3 3 13AI 4 4 14Si 2, 8, 4 15P 2, 8, 5 5 -3 Non-metallic : Gains electrons with 16S 2, 8, 6 6 -2 radicals. ease to form electronegative 17C| 2, 8, 7 7 -1 18Ar 2, 8, 8 8 Inert:Does not loseor gainelectrons. Properties bonds/ionicbonds : of electrovalent (1) Ionicbonds areformed by lossor gain of electronsbetween dissimilar atoms. (2)Thistype of bonding generallytakes placebetween a metal and the non-metal. (3)Ionicbonds are non-directionaland extend inallthe directions(threedimensionalstructure calledan ioniclattice). (4)Due to strong intermolecular forcesof attraction, ioniccompounds have high meltingand boiling points. (5)Ioniccompounds are more solublein water because they have ion-dipole interaction in water. (6)Sinceionicbonded compounds are ionisedin the fused as wellas in solution state,they conduct electricity. (7)Ioniccompounds are polarinnature (forexample,in NaCl compound Na is+ve pole while CI is-vepole). Examplesofionicbond formation: (i) Formation of MgO: Mg-atom A = 24, Z = 12. Electronic configuration2, 8, 2.  : BasicSclence Chemistry(Sem. ) 1.5 ChemlcalBonding Number of valenceelectrons 2, To attainstableconfigurationof nearestinertgas Ne (Ne - 2,8), electronsand becomes an lon Mg-atom losesitstwo valence with two positivecharges (Mg). Oxygen atom -A= 16,Z = 8, Electronconfiguratlon 2, 6. Number of valenceelectrons 6. To attain stableelectronicconfiguration of nearestinertgas Neon (Ne = 2, two electronsgiven up by the Mg-atom, 8),O-atom galns resultinginthe formationof a negativeoxide ion[O J. O+ 2e (2,6) (2,8) Hence only one O-atom is requiredto take up both the electronsgiven up by the Therefore a molecule of magnesium oxide is Mg-atom. made up of one magnesium ion (Mg*) Oxygen ion (0) held togetherby an and one electrostatic forceof attraction (an electrovalent or ionic bond). Mg* +[ö:] MgO 2, 8, 2 2, 6 2, 8 2, 8 Magnesium Lends 2 Gains 2 Neon Neon oxide molecule electrons electrons confi. Confi. Formationof sodium chloride (NaCl) molecule: 1.A mnolecule ofsodium chloride(NaCl)consistsof one atom of sodium and one atom of chlorine. 2. Sodium atom (Atomic Number= 11) has an electronicconfiguration(2,8, 1)and chlorineatom (AtomicNumber = 17) has an electronicconfiguration(2,8, 7). 3.Duringthe formationof sodium chloride, sodium atom loosesitsvalence electronto chlorine atom and forms Na ion.When chlorine atom accept this electron, itforms CI ion. 4. These two equal and oppositelycharged ions (Nat and CI ions)which are produced,bound togetherby the electrostatic forcesof attraction to form sodium chloride(NaCl). Na x + + NaCI (2,8,1) (2,8,7) (2,8) (2,8,8) 2. Covalentbond : Covalent bond is formed by mutual sharing of electrons in pairsbetween two similar or dissimilar atoms,both of which make equal contribution of electrons. In covalentbond, there is no loss and gain of electrons,(hence, no electrical charges are developed) only sharing ofvalenceelectronstakes place. These shared electronsbecome common propertyof both atoms and accountforthe stability of both atoms i.e., both atoms acquirestableconfiguration. Sharingof electronstakes placeby followingthreeways : (1)When a covalentcompound isformed by mutual sharingof 'one pair' of electronsbetween two atoms,itiscalled covalentbond' representedas (-). a 'single e.g.H2, Clz,H0, NH3, CH4 etc. (i) When a covalent compound isformed by mutual sharingof two pairsof electronsbetween the two atoms,itiscalled 'doublecovalentbond' representedas (=). e.g.O2, CO2, CzH4 etc. (ii)When a covalentcompound is formed by mutual sharingof "three pairs'of electrons between the two atoms,itiscalled a 'triple covalentbond' representedas (=). e.g. N2, CzH2 etc. Formationof covalentcompounds : ) Singlecovalent bond compounds : Such molecules are formed due to mutual sharingof one pairof electronsbetween similar dissimilaratoms. or  1,6 Chemlcal Bondine (Sem. l) Sclence:Chemistry Baslo ()Formation H,0: of one atom ofoxygen. two atoms of hydrogen and moleculecontains Water 2, Z = 1. H-atom A = electron1, Number of valence itsduplet. Each H-atom isin short 1 of electronto complete A = 16,Z = 8. Each O-atom Electronicconfiguration2, 6. - electrons= 6. Number ofvalence 2 electrons to complete itsoctet. O-atom isinshort of O-atom completes its octet by sharingtwo Therefore in the formation of H,0 molecule, completes itsdupletby sharingone eloo each H-atom electrons with two H-atoms. Similarly are formed between hydrogen and two separate single covalent bonds with O-atom. Thus, bonds Oxygen atoms. Singlecovalent HLoH H,0 (2) (2,8) (2) (1) (2.6) Formationof Cl,: (ii) Each Cl-atom A = 35, Z = 17. Electronicconfiguration 2, 8, 7. Number of valenceelectrons 7 contains 7 valenceelectrons of chlorine e In the formationof chlorinemolecule,each atom complete itsoctet.Hence two Cl-atomscombine te each Cl-atom is inshortof one electronto is developed Therefore,singlecovalentbond form a moleculeby sharingone pair of electrons. between them. bond Singlecovalent (2, 8, 7) (2, 8, 8) (2, 8, 8) Double covalentbond compounds : of electronsbetween similar or Such moleculesare formed due to mutual sharingof two pairs dissimilar atoms. e.g. (i) Formationof O, molecule : Oxygen moleculeisdiatomic. Each O-atom A 16,Z = 8. = Electron configuration= 2, 6. Number of valenceelectrons= 6. Each atom of oxygen isinshortof two electronsto complete itsoctet. Thus O, moleculeisformed by sharingtwo pairsof electrons between two atoms of oxygen by completingthe octetof each. Two shared pairs form a double covalentbond. (2, 6) Double covalent bond (2,8) (2,8) (ii) of Co, molecule: Formation InCO, molecule,one carbonatom combines with two oxygen atoms. C-atom A = 12,Z = 6. Electronic configuration = 2, 4. Number of valenceelectrons= 4. Carbon atom isinshortof 4 electronsto complete itsoctet. BaslcSclence :Chemistry (Sem. ) 1.7 Chemical Bonding Each O-atom A = 16,Z = 8. Electronicconfiguratlon2, 6. Number of valenceelectrons= 6, Fach O-atom isin shortof two electrons to complete theiroctet. Hence, carbon dioxidemolecule isformed by two oxvgen atoms sharingtwo pairsof each with a carbonatom. electrons Thus, two double covalentbonds are formed inthe formationof CO, molecule. oCF0CO, (2, 4) (2, 6) (2, 8) (2.8) (2,8) Double covalentbonds Triple covalentbond compounds : Such molecules areformed due to mutual sharingof threepairs of electrons between similar dissimilar atoms. or (i) Formationof N, molecule: Nitrogenmolecule isdiatomic. Each N-atom -A = 14,Z = 7. Electronic configuration 2, 5. Number of valenceelectrons= 5. Each N-atom is in short of 3 electronsto complete the octet..So both N-atoms contribute 3 electronsforsharing. Thus, N, molecule isformed by sharingthree pairsof electron between two atoms of nitrogen and hence comnpleting the octet of each. Three sharedpairsof electronsform a triple covalentbond. 2 EN:ENN: NAN N (2,5) (2, 8) (2,8) Triplecovalentbond (iü) Formationof C,H,(acetylene) molecule: Acetylenemolecule consistsof two atomns of carbon and two atoms of hydrogen. Each C-atom A = 12, Z = 6. Electronic = 2, 4. configuration Number of valenceelectrons= 4. Therefore,each C-atom isinshortof 4 electrons to complete the octet. Each H-atom -A = 2, Z = 1. Number ofvalencyelectron= 1. Each H-atom isinshortof one electronto completethe duplet. Thus,acetylene molecule is formed by sharingthree pairsof electronsi.e.formingtriple covalentbond between two carbon atoms and one pairof electronsi.e.singlecovalentbond with each hydrogen atom. (2, 4) (1) (2) |e, 8) (2) H-C=C-HC,H Properties ofcovalentbonds : (1)Covalentbond isformed between two atoms by sharingof an electronpair. (2)Thistype of bond isusually formed between two non-metalatoms. (3) Covalentbonds arerigid and have directional nature. (4)Covalentbonds aremore strongerthanionicbonds. (5) Covalently bonded compounds have low melting and boiling points.  1.8 chemical Bondin (Sem. I). hence do not BasleSclence: Chemistry water. They do not ionise, are insoluble in condug (6)Covalent compounds electricity. isno chargeseparation. are non-polar innatureas there (7)Covalentcompounds bond : 3. CoordinateorDative electronsare contributed by one type of covalent bond in which the shared of electrons atom Itis a special theirsharing without any contribution accepts for sharing,is only;whilethe otheratom calledthe (calledlone-pair) contributes electron-pair acceptor. donor;, shared electronsiscalled which The atom accept these by an arrow head (), starting which while the other atom from represented coordinate or dative bond is,generally the The acceptor. donor and endingatthe :Ä:B: or A B B: Coordinate :A: Acceptor atom, or (Donor atom, Lone pair dative configuration) stable (2e shot of (one side bond configuration) shared electronpair) possibleonly between an atom,with coordinatecovalent bond is Therefore,the formation of a or ion that needs a pair of electrons in itsvalence shelland an atom an unshared to acquire a stableconfiguration. electrons An unshared electron The main difference pairpresentinthe valence shell between the coordinatebond and of an atom iscalled a lone pair. the covalent bond is in the mode. Once established, they are indistinguishable. formation. donor to the acceptorwhil Coordinatebond is representedby an arrow,pointingfrom the covalentbond isrepresentedby a line. (NH)is an covalentbond example of co-ordinate Example :Formation of ammonium ion formation. The bonds inammonia (NH) areof covalenttype. molecule itself electronpair(lone pair).Duringthe In ammonia (NH3),nitrogenatom containsone unshared lone pairof electronto form a formationof (NH)ammonium ion,nitrogenatom providethis coordinatebond with hydrogen [H"]ion. N: + H H-N:H Hydrogen H ion Ammonium ion Ammonium molecule givesa unit positive Because NH, isa neutralmolecule,the union with hydrogen ion (proton) ammonium charge to the resulting ion. Other examples areCo,N,0,HNO3, H,S04, O3 etc. Example:Formationof (OH,)* ion: Thision isformed by the combination of Hz0 molecule and Ht ion.In H,0 molecule,O-atom is bonded to two hydrogen atoms by two singlecovalent bonds. ThisO-atom containstwo lone pairs of electrons. During the formationof hydronium ion,one of the lone pairof electronon O-atom (Donor)isdonated to electrondeficient to form a newO H, co-ordinate Ht ion (Acceptor) bond. Coordinate bond Lone pair :0+H t Acceptor H Fig. 1.1  : BaslcSclence Chemistry(Sem, I) 1.9 ChemlcalBonding Propertiesof coordinate bond: (1) The bond lsrigid and directional. (2)Coordinatecovalentbond isthe property of atoms that have lone pairof (3)In all electrons. cases, cOordinatebond isa covalentbond. The merely serves to indicatethe origin prefixdipolar, dativeor coordinate of the electronsused increatingthe bond. (4)Often these type of bonding isfound in complex chemicalcompounds. (5)Coordinatecovalentbond compounds have following : properties (i)Theirmeltingand boilingpointsarehigherthan purelycovalentcompounds and lowerthan purelyioniccompounds. (i)These are sparinglysoluble in polar solventlikewater but solvents. readilysolublein non-polar (ii)Like covalentcompounds, these are also bad conductors of electricity. Theirsolutionsor fusedmasses do not allowthe passage to electricity. 3. Hydrogen bond : hydrogen bond is a type of electrostatic forceof attraction A between an electronegativeatom (likenitrogen,oXygen and fluorine) and a hydrogen atom bonded to another electronegative atom. Or when hydrogen atom is covalentlybonded to a stronglyelectronegativeand small-sized atom (such as nitrogen,oxygen and fluorine),the shared electron pairbetween the hydrogen atom and the stronglyelectronegativeatom liesmuch more nearerto the electronegative atom. Thisresultsinthe development of partialioniccharacter inthe covalentbond, with a fractional positivechargeon the hydrogen atom, and a fractional negativecharge on the electronegative atom. Example: (HF)molecule,the fluorineatom acquiresa fractional In hydrogen fluoride negative charge whilehydrogen atom acquires a fractional positivecharge. Thus H+F: H: H-F (1) (2,7) Sharedelectron Hydrogen and fluorine pairlies much atoms acquirerespectively nearerthe electro fractional positive and negativeF atom negativecharge.Thus HF isa polarmolecule. Such a moleculeissaidto be polarand behaves asa dipole. Thus, when two HE_ molecules approach closely, an electrostaticattractionbetween the fractionalpositivelycharged H atom of one HF molecule and fractionalnegativelycharged F-atom of the other HF molcule takesplace.Thisattractiveforcebetween the two oppositely charged atoms of two molecules leadsto the formationof a weak bond, calledas hydrogen bond orhydrogenbridge. Thus Hydrogen bond Even more than two moleculesmay associate togetherto form largeclusterof molecules. e.g.... Ht – F..Höt -F..Hot - F The cluster of HF molecule isrepresented as (HF)n. (......). The hydrogenbond isdenoted by a dotted line The hydrogen bond may be : 1.Intermolecular : ie.involvingthe electrostatic forceof attraction between hydrogen atom and an atom of electronegative element of two different molecules. Example:p-nitrophenol, (HF)n,H,0.  1,10 ChemlcalBonding (Sem.I) BasicSclence:Chemistry :.e. involvingthe 2. Intramolecular of electrostatic force attractlon + Hydrogen bond H-atomn and an zlnio between atom, both presentin electronegative the same molecule. O-nitrophenol o - chlorophenol Example : o-chlorophenol o-nitrophenol, Characteristicsof hydrogen bond : a hydrogen atom. (1) This bond alwaysinvolves element wh:ak. electronegative (2)Hvdrogen bond isformed between H atom and atom of an small insizeand highlyelectronegative. or withinpartsof a cina (3)Hvdrogen bond can occur between molecules (intermolecular) molecule(intramolecular). (4) A hvdrogen bond is weaker than covalentbond or ionicbond but stronger than Van der Waals forces. innature,consequently compounds (5)Itis electrostatic containinghydrogen bonding are polar. partially (6) The presence of hydrogen bonding in compounds is indicatedby highermelting points points,due to associationof molecules. boiling (7)Intermolecular hydrogen bond forms bridgebetween two molecules. a (8)The strengthof cement concrete and accumulationof water in plantsand animal bodies ie due to hydrogen bonding. 4. Metallic bond : The metallicbond isa type of chemicalbond thatoccursbetween atoms of metallic elements. A metallic bond is totallydifferentfrom covalentand ionicbonds (bonds between just twO atoms). Insteadof a bond between just two atoms, a metallic bond is a sharingof electrons (valence electrons) between many atoms of a metallic elementpresentin metal lattice. Thus, metallicbonding isthe electrostatic attractiveforce between valenceelectrons(inthe form of an electroncloud of delocalizedelectrons) and positivelycharged metal ions (called kernels)ina metal element. Itmay be describedas the sharingof free electronsamong a lattice of positively charged ions (cations). Hence, allvalenceelectrons belong to the crystalas a whole.These electrons arefree to migrate through the crystallattice,thereby givingriseto high electrical metals. conductivity to Example : Metallic bonds are seen in pure metals (sodium, etc.)alloysand some metalloids. aluminium,copper, silver, gold Metalions (positively charged kernels) Sea of valence : Fig.1,2 Schematic electrons illustration of metallic bonding  RaslcScence : Chemistry(Sem. I) 1.11 ChemicalBonding Itisshown in the above diagram,the valenceelectronsbecome dissociated with theiratomic core and form an electron'sea' that acts as the bindingmedium between the positively charged ions. of metallic Characteristics bonds : (1) Metallic bonds arenon-directional. (2) Metallicbonding accOunts for many physicalpropertiesof metals such as metallic luster, electrical conductivity, thermalconductivity,malleability and ductility, high tensile strengtn, hardnessopacity, high meltingand boilingpoints. (3)Metallic bonds, being strong,sothe metalshave moderatelyhigh meltingpoints. (4)The strengthof metallic bond is directlyproportionalto the number of valence electrons presentin the outermost shellof an atom of an element whileit isinverselyproportional to the sizeof an atom of an element. Metallic properties : Metals have following physicalproperties,which can be explainedon the basisof bonds metallic : 1. Metallicluster : The brightlusterof metal is due to the presence of delocalizedmobile electrons which absorb photons of light,when lightfallsonthe surfaceof the metal,and get excited. These excitedelectronsget promoted to higher energy leveland readily returnfrom the higher to lower levelsof energy by releasingenergy, thus becoming a source of light radiations. As a resultlightappearsto be reflectedfrom metal surfaceand the surfaceacquiresa shiningappearance,which isknown as metallic luster. 2. Electrical : conductivity The presence of mobile electronscauses electrical of a metal.When a potential conductivity differenceisapplied acrossthe metal sheet,the freemobileelectronsinthe metalliccrystal startmoving towards the positiveelectrode. The electronscoming from negativeelectrodesimultaneously replacethese electrons. Thus, the metallic sheet maintains the flow of electronsfrom negativeelectrodeto positive electrode.Thisconstitutes electrical conductivity. 3. Thermalconductivity : When a partof the metal isheated,the kineticenergy of the electrons inthatregionincreases. Since the electronsarefree and mobile,these energeticelectronsmove rapidly to the cooler part andtransfertheirkineticenergy by means of collisions with other electrons. Therefore,the heat travels from hotterto coolerpartsof metals. 4. Malleability and Ductility : Metals can be beaten into sheets (malleability) and drawn into wires (ductility). Metallic bonds arenon-directional innature. Whenever any stressisappliedon metals, of adjacentlayers the position ofmetallic kernels isalteredwithout destroyingthe crystal. The metalliclattice gets deformed but the environment of kernelsdoes not change and remainsthe same as before. The deforming forcessimplymove the kernelsfrom one lattice siteto another. High tensile strength: i. Metalscan resiststretching withoutbreaking. A attraction strongelectrostatic between the positivelycharged kernelsand the mobile electronssurroundingthem isthe reason forhigh tensile strength.  Baslo olenoe Chemistry (Gem. I) 1.12 ChemicalBonding 6. Mardnessof metals The hardness of metalsisdue to the strengthof the metalllcbond. le general, bond depends upon : the strengthof a metallic (1) The greaterthe number of valenceelectronsfordelocallzation, the strongerIsthe metal. bond. (2) Smallerthe size of the kernelof metal atom, greaterIs the attraction for the delocallzes Consequently,strongerIsthe metallic electrons, bond, that fals 7. Opaqueness :The light on metals iseitherreflected or completelyabsorbed by the delocallzed electrons, isable topass through metalsand they aretermed as opaque, no light Because of this, 8. Meltingand Bolingpoints: Metals have metalllcbond strengths,which isintermediatetothat of covalentand lonic bonds. Thereforein general,metals have boiling and meltingpointsln between to that of covalent and lonlccompounds. Comparison of Ionicbond,Covalentbond and Metallic bond : Ionicbond Covalentbond Metallic bond 1, Thetransfer of electrons Thisbond Isformed by mutual Thisbond Isformed due to the between two atoms having sharingof electrons between attractionbetween kernelsand different electronegativities atoms of same ordifferent the mobileelectronsina metal forms thlsbond. elements. lattice. 2.Thisis a strongbond due to Thisisalsoa fairly strongbond Thisis a weak bond as forceof electrostatic because theelectronpalrIs compared to lonicbond due to & attraction. stronglyattractedby two thesimultaneousattractionof nuclel. the electrons by a largenumber of Kernels. 3. ThisIsa non-directlonal ThisIs a directlonal bond. Thiss non-directional bond. bond. 4. This bond makes substances Thisbond makes substances Thisbond makes substances hardand brittle. hard and incompressible. malleableand ductile. 5. Such bond forms between Such bond isformed between Such bond occurswithinposltive dissimllar atoms. similar or dissimilar atoms. metal ionsand delocalized electrons. Van der Waals orIntermolecular forces: ItIsa weak forceof attractionbetween electrically neutralmolecules thatcollide with or pass verycloseto each other. The Van der Waals forceIscaused by temporary attraction between electronrich regionsof one molecule and electron-poorregions of another.These attractions are very common but are much weaker than chemical bonds. Similarly, electronrlch regionsof one molecule are repelledby electronrichregionsof another molecule. Therefore,Van der Waals forcesare sum of the attractive and repulsive forcesbetween atoms and molecules. These forces differfrom chemical bonding because they resultfrom fluctuatlons in charge densityof particles. The magnltude of this force is found to be maximum in solidsubstance and minimum in gaseous substance, BeslcSclence:Chemistry(Sem. I) 1.13 Chemical Bonding These forcesof attraction depend upon: 1, Size of the nmolecule, 2 Number of electronspresentinthe molecule, 3. Average distancebetween two molecules. 4. Surfaceareaof the molecule, The three common types of Van der Waals forces (intermolecular forces),listedbelow from weaker tostrongestare: 1.London dispersionforces :The weakest intermolecularforces arisefrom temporary charge development thatoccurs spontaneouslyinall compounds, even in neutralatoms due to uneven distribution of electrons.This makes one side of the atom more negatively charged than the other.Itiscommonly observed in halogenslikeF2, I,and nobel gases like He, Ne, Ar and molecules like CO,. Instantaneous Instantaneous Induced uneven distribution dipoleon dipole of electronsinHe-atom neighbouring He-atom. Resultant attractiveforce Fig.1.3 2. Dipole-Dipole : forces ModeratelystrongVan der 8 Waals forces,occur among substances with permanent, although partial charge development. e.g.HCI acidexperiencesdipole-dipole attractions. Neither the H-atom nor the Cl-atom have full charges,but they do have differentelectron Dipole-dipole interaction densities,which gives rise to partialcharge Fig,1.4: Dipole-dipole interaction development. 3. Hydrogen bonding : Itisthe strongestof Van der Waals forces,isan especiallystrong force.Hydrogen boding arisesonly between molecules that have type of dipole-dipole hydrogen atom directlybonded to a veryelectronegativeatom (such as fluorine, oxygen or nitrogen), which enhances the partialcharge development. : Example Water molecule is a greatexample of hydrogen bonding, which accountsfor many unique propertiesofthisuniversal solvent. +8 H +8 Characteristics ofVan derWaalsforces: Itsmain characteristicsare : (1)They areweaker than normal covalentand ionic bonds. (2)Van der Waals forcesareadditive and cannot be saturated. (3)They have no directional characteristic. (4)They areallshort-range forcesand hence only interactions between nearestparticles need to be considered (instead of all particles). Van der Waals attractionis greaterifthe molecules arecloser. (5) Van der Waalsforcesare independent of temperatureexceptdipole-dipole interaction. 12 MOLEGULARARRANGEMENT Matter has the unique propertyof existingin differentstates at different temperature and pressure. and gas arethe threestatesof matter. Solid,liquid and solidsareall Gases, liquids made up of atoms, moleculesand/or ions,but the behaviourof theseparticles differinthe three phases.Fig.1.4illustrates the differences.  BasleSclence:Chemistry (Sem.I) 1.14 Chemlcal Bonding B Intermolecular Intermolecular Intermolecular structure of solid structure of liquid structure of gas Fig.1.5 1.2.1 Arrangement inSollds The particlesina solidarepacked closeto each other. The onlymovements they make are smallvibrationsabout theirfixedpositions. The spaces between particlesare known as in solids.Due to this, intermolecularspaces.These are almost the particlesattracteach other very stronglyand particlesisnot possible. That iswhy solidsarerigidand retaintheirshape. negligible free movement E Example :Metals,ionic solidsetc. 1.2.2 Arrangement inLiqulds| The particles inliquidscan move about a little. They arelesstightly packed than insolids. They have biggerintermolecular spaces,as compared to solids. The particles ofliquidsdo not have fixedpositions. The intermolecularforcesof attraction between the particles of a liquidareweaker than those in solidsand hence movement of fixed positions,not rigid particlesispossible. That iswhy particles and do not have theirown shape. of liquiddo not have container. They take the shape of the Example:Water, alcohol, kerosene etc. |1.2.3 Arrangement in Gases The particles ingases arefarapartfrom one another. They have huge intermolecular spaces between their particles. There arealmostno intermolecular attraction holdingthem together. The particles collidewith each other and move inall Hence the gas has neithera directions. definites hape nor a definite volume.Example:Oxygen, Chlorine, Airetc. Liquidsand solidsare often referredto as closetogether. condensed phases because the particles arevery Gases and liquids arecalled fluidsbecause of theirabilityto flow. The following tablesummarizespropertiesof gases, liquids and solids. Table1.2 Gas Liquid Solid 1.Gas assumes the shape Liquidassumes the shape of the Solidretains and volume of its a fixedvolume partof the containerwhich it containerto because and shape because of closely Occupiesbecause particles can packed particles. particles can move past move/slidepast one another. one another. 2. Gases arecompressible Liquids arenot easily Solidsareleastcompressible due to lotsof freespace compressibledue to little free due to little freespace between particles. space between particles. between particles. 3.Gas flowseasilysince Liquidflowseasily because Solidsdo notflow because particles can move past particles can move/slide past one particles cannot move/slide one another. another. past one another. BasicSclence : Chemistry(Sem. I) 1.15 Chemlcal Bonding STRUOTURE OF SOLIDs Solidsare substances characterised by definiteshape,definitevolume,non-compressibili Veryslow diffusion, rigidityand mechanicalstrength. The atoms,molecules or ions(particles) insolidsare closely-packedand they areheld together by strongforcesand hence, cannot move about inrandom. Solidsmay be describedas eithercrystallineor amorphous. () Crystal : solids Crystalline slidsare those which existin welldefined crystalline with theirpartilesarrangedin a certaindefinitegeometricalpattern, forms, throughout the three dimensionalnetwork of the crystal. Thus, they have long-rangeorder.e.g. sulphur, sugar, sodium chloride,diamond etc. (i) Amorphous solids: They are pseudo solids. They have completely random particle arrangement. Thus they lacka long-rangeorderin theirstructure. Infact, amorphous solids (meaningwithout form)can be regarded as supercooledliquids, havingsmallstructural unit with a short-rangeorder.However, unlikeliquids (orstiffness), they have rigidity due to theirhighlyenhanced viscosities. e.g.Glass,rubber,plastic,pitch (resin) areamorphous solids. solids Crystalline aresolidsintruesense. pifferencebetween Crystalline and amorphous solids: Sr.No. solids Crystalline Amorphous solids 1 They have definite arrangement of They have random arrangement of atoms,ionsor molecules. atoms,ionsor molecules. 2. They have sharp melting points. They do not have sharp melting points. 3. They have definitegeometry. geometry. They do not have definite 4. They areanisotropic. They areisotropic. 5. Cleavage isuniform. isnot uniform.Knife Cleavage ct op 6. Examples:Sodium chloride,diamond, Examples:Glass,rubber,plastic.tau graphite,etc. ate alas Classification of crystalline solids based on bonding : Solids Amorphous Crystalline lonic Metallic Covalent Molecular (NaCl,KCI, (Cu,Ag, Au) CsCI,ZnS) Two dimensional Threedimensional (Diamond) (Graphite) Polar Non-polar (Water,Sugar) (,S, P) Fig.1.6  ) BasicSclence :Chemistry(Sem. 1.16 ChemicalBonding Based on the nature of forcesbindingthe constituentsunit,crystalline solidsare classie broadlyintofollowing fourtypes. 1.Ionicsolids :Consistof an arrayof positive and negativeions arrangedin acharacteres. pattern, lattice. throughoutthe crystal e.g.NaCl,CaO etc. : 2. Covalent solids Consistof an arrayof atoms that share electronswith neighbouriee atoms, so that the atoms are linkedtogetherby a continuous system of strongcovalen only.e.g.Diamond,graphite, bond, which extend infixeddirections silicon etc. 3.Molecularsolids strongt :Itinvolvesweak Van der Waal'sbonding which issufficiently (usually hold the particles molecules)together.e.g.Iodine(I;), solidCO, solidN,etcC. 4. Metallic solids:Solidcontainingmetallicbonding consistof positivemetal ions (called kernels)ina cloud of valencyelectrons(referred as electronsea). The bindingforceisthe attraction between the positivemetal ions and the electroncloud x The valence electronsmay be consideredto belong tothe metallic solidas a whole and thesearefreeto migratethroughoutthe crystal lattice. and Unitcell Crystallattice : Crystallattice(structure)is a highly ordered three-dimensionalstructure, formed by its constituent atoms ormoleculesor ions. Crystalstructuremay be convenientlyspecified by describingthe arrangementwithinthe solid of a small representativegroup ofatoms ormolecules,calledthe 'unit cell'. Therefore,unit cellisthe smallestbuildingunit of a crystallattice which,when repeated in different directions(threedimensional), generatesthe entirecrystallattice. 4Z b a Unitcell 1.7: Fig. and crystal Unit cell lattice Innature,7 different types of crystal structures arefound. or lattices The simplestcrystallineunit cellto pictureisthe cubic,where the atoms are linedup in a square,threedimensionalgrid. The unitcellissimplya box with an atom ateach corner. Simple cubic crystalsare relatively rarebecause they tend to easily distort. However many crystalsform body-centered-cubic(bcc)or face-centered-cubic(FCC) structures,which are cubicwith eitheran extraatom centeredinthe cube orcenteredin each faceof the cube. In cubiccrystal, a the intercepts on the threeaxes areequal and all the anglesareequalto 90°. The crystallinesolidshave definiteorderly arrangementof theirconstituentparticles in three dimensions. The positionofthese particles ina crystal, relativeto one anotherareusuallyshown by points,The arrangementof an infiniteset of these pointsiscalledspace lattice. Latticepoint:In a crystallattice, each molecule/ion/atomisrepresentedby a single point. Thispointwhích representsthe positionof constituent particles(molecule/ion/atom)ina crystal iscalledas latticepoint.Incrystallattice, lattice pointsarejoinedtogetherby straight lines. BasleSclence :Chemistry (Sem, I) 1.17 One dimensionallattice : points All thelatticepointsare ChemicalBonding presentalong only (X). one axis X -axis Fig.1.8 TWo dimensional lattice points: Latticepoints X and Y axes. arepresentalong two mutuallyperpendicular Fig.1.9 Three dimensional lattice points:Lattice points are present along perpendicular axesX, Y and Z. three mutually Y -axis b X axis Z-axis Fig.1.10 or Crystal Space lattice lattice : crystallattice isa highly ordered set of constituentparticles in three dimensions.These A constituentparticles mnay be atoms or ionsormolecules. It is "an arrangement of latticepoints showing how constituentparticles (atoms,ions or molecules)of a crystalarearrangedat different positionsinthreedimensionalspace". Allthe crystal lattice are builtup by a particular repeatingarrangementof constituentparticles (atomsorionsor molecules) throughout the crystal. Unit cell: Itisdefined as the smallestbasicthree dimensionalrepeatingunitwhich when repeatedin directions different produce the complete crystal lattice. Unit cellshows the shape of the entire crystal. The complete crystal lattice can be obtainedby inall extending the unit cell the three directions. Unit cellthus issimplya box in which paticles may be locatedatcorners, facesand centreof the boX.  1.18 (Sem. I) BasieSclence Chemistry : Chemica cell: ParametersofUnit by The unit cells characterlzed Be edgesa,b andc.. lengths alongthree its edges between the pairsof the anglesa,B, y B (a) (b) Fig. 1.11 Types ofUnitCells Primitiveor Non-primitive or Simple unitcells Centered unitcells Inthem pointsor particlesare Inthem pointsorparticlesare present not only presentonly at corners at corners but als0.at some otherpoints Body centeredunit Face centered unit End centeredunit cell cell cell Particles are presentat Particlesare presentat Particlesare present Corners as wellas atthe body Corners aswellas at the at cornersas well as centre centre of each face at centreoftwo opposite faces Fig.1.12 Types of Crystal Systems: Depending upon edges a, b, cof unitcelland different types of crystal angle a, B. y between them, there structuresor lattice found in are seve nature.  : Rasle Sclence Chemlstry(Sem.I) 1.19 Chemlcal Bonding Typesof CrystalSystems Cubic Tetragonal 4 Rhombohedral Orthorhombic a =bc a =bC or Trigonal a b*c a =ß=y=90° a=p=y= 90° a=b=C a =y=90,B 90 a =ß=y = 90 Hexagonal Monoclinic. Triclinic a=bc a=B=90° a#b#c a=y=90 abC Y= 120° aBy 90 B 90° Fig.1.13 Most metals and many other solidshave unitcell structuresdescribedas SimpleCubic (SC), Body Centered Cubic (BCC),Face Centered Cubic (FCC) or Hexagonal Closed Packed (HCP). However, the structure can change depending on temperature. 1.SimpleCubic (SC)orPrimitive Crystal Lattice: Simplecubicunit cell has atoms ateach of the eightcornersof a cube. Each atom inthisstructure can form bonds to itssixX nearestneighboursthat isfourinitsplane, one atom inthe layerabove itand one inthe layerbelow it. Therefore,itissaidto have a coordination number of 6. Inthisstructure, an atom situatedat any cornerof each unitisshared by a totaleight unit cells. of all Thus each unit cellhas 1/8shareof every corneratom. So the totalcontribution the eight corneratoms to each cell 1 1atom. =x8= So simple unitcellconsistsof 1atom per cell. Simplecubic(SC)structure isfound in crystallattice of Polonium metal, NaClsolid. : Fig.1.14 Simplecubic(SC)lattice  1.20 BasioSclence:Chemistry(Sem. I) 2. Body Centered Cubic (BCC)Structure : ChemicalBa The BCC unit cellhas atoms at each of the elghtcornersof a cube (likecubic unitcell) plus one atom in the centre of the cube (left image below). Each of the corner atoms isthe corner of another cube, So the corner atoms are sharedamong eightunitcells. Itscoordination number of 8 because each atom touchesfouratoms inthe layerabove itand fouratoms inthe layerbelow it. :BCC Fig.1.15 structure 1(contribution x8 number of of) Totalnumber ofatoms presentinBCC = Corneratom Corners + 1atom at centre = 2x8+ 1= 2 So BCC unit cell consists of twO atoms per cell. The bcc arrangement does not allowthe atom to pack together as arrangements. as the closely fccor to bcc structure is often the high temperatureform of metalsthat are temperature. close-packed at Metals having bcc structure areLi,K, Na,Cr,Ba, V, a-Fe and W. Such mnetalsare usuallyharderand lessmalleable. 3. Face Centered Cubic(FCC)Structure : The face centeredcubicstructure has atoms located at each of the cornersand the centresof allcubic faces(leftimage below). Each of the corner atom is the corner of another cube, So the corner atoms are shared among eight unit cells. Additionally, each of its six face centeredatoms is sharedwith an adjacentcell. Itscoordinationnumber is 12 because each atom touches four atoms in itsplane,four atoms in the layerabove itand fouratoms inthe layer Fig.1.16 : FCC structure below it. Totalnumber of atoms presentinFCC is 1(contribution of) corneratom x8 (number of +(contribution atom of at) number) Corners centreof face x6 of faces -Gx8 +x6= 1+ 3 = 4 So FCC unitcellconsists offouratoms perunitcell. Inthe FCC structure(andthe hçp the atoms can pack closertogetherthan they can structure), inthe bcc structure. The atoms from one layernest themselves in the empty space between the atoms adjacentlayer. To understandpackingarrangement, aligned in imaginea filledwith layer of ballsthat are box balance columns and rows. When a few additional ballsare tossed inthe box, they willnot create on top directly of the inthe balls first layerbut instead will come to restin the pocket  : Raslo Sclence Chemistry(Sem. I) 1.21 ChemlcalBonding between fourballsof the bottom layer. As more ballsareadded they will pack togetherto fiil up allthe pockets. Some of the metals thathave the FCC structureincludeAl,Cu, gold,iridium,Pb,NI,Pt and silver. A. Hexagonal ClosePacked : (HCP)Structure Anothercommon closepacked structure isthe hexagonal closepacked structure. The total number of atoms presentinHCP (contributionof 1 6 atom at cornerx12 (number of atoms contribution present of atom at (numberof atoms of hexagon \present a t corner 2 x +3 present inside 1 +5x2+3 2 =AX 1 12 = 2 + 1+3 = 6 \centreof top/bottom/ hexagon So HPC unit cell consistsof sixatoms per unitcell. The hexagonal structureof alternating layersisshifted,so itsatoms are alignedto the gaps of the precedinglayer. The atoms from one layernest themselves in the empty space between the atoms of the adjacentlayerjustlikein the fccstructure. However,insteadof beinga cubicstructure, the patternishexagonal. The hcp structurehas three layers of atoms. : Fig.1.17HCP structure In each top and bottom layer, there are sixatoms that arrangethemselves in the shape of a hexagon and a seventh atom that sitsinthe middieof the hexagon. The middlelayer has three atoms nestleinthe triangular'grooves'of the top and bottom plane. Note thattherearesixof these "grooves"surroundingeach atom in the hexagonalplane,but onlythree of them can be filledby atoms. The coordination number of atoms-inthisstructureis12 because each atom issurrounded by sixnearestneighbours inthe same close packed layer, three inthe layerabove and threeinthe layerbelow. The hcp structureisvery common formetals including beryllium, Cd, Mg, titanium, zincand zirconium. Physical properties that result from the structure ofmetals: The structure of metalscan be used to explain many of the characteristic physicalpropertiesof metals like: (1)Luster. (or solidness). (2)Rigidity (3)Malleability and ductility. (4)Electrical and thermal conductivity. (5)Meltingand boiling points. [Already bond formation.] discussed in metallic BasicScence :Chemistry(Sem. I) 1.22 Chemical Bonding ImportantPoints B Exstence of an atom issuggested2000 years back by AcharyaKanad. ordissimilar Moleculesareformed by certain kindof chemicalbonds between similar at Valenceelectrons take part inchemicalbond formation. The electrons presentinoutermostorbitof an atom areknown as valenceelectrons Chemicalbonds areformed by : ()Transferofelectrons(loseorgain)forms electrovalent bond orionicbond. (ii)Mutualsharingof electrons forms covalentbond. (üi) One sidedsharingof electrons forms coordinatebond. (iv) Delocalization of electrons throughmetal lattice forms metallicbond. (v)When H-atom acts asa bridgebetween two electronegative atoms forms hydrogen hee. Chemical bonds accountforphysicaland chemicalproperties of moleculesor compounds Matter occurs in three states:solids, liquidsand gases depending upon the intermolecular forcesholdingthe particles (molecules/atoms/ions) together. strength of Solidstate may be describedas crystallineoramorphous. In crystalline are arrangedin definitegeometricalpattern while in solids,particles solids,particlesarerandomly arranged. amorphous Metallicsolidisa type of crystalline solidin which positivemetal ion (kernel) isbounded hu metallicbond (forceof attraction)to valenceelectrons forming crystal lattice. Unitcellisthe buildingunitof crystal lattice. The structureof unit cellsare described as simple cubic body centered cubic (bcc),ace centeredcubic(fcc)and hexagon-closedpacked (hcp). Physicalproperties of metal likehardness,tensilestrength, malleability, ductility, conductivihy can be explainedbetterby structureof metals. Practice Questions 1.Writea shortnoteon electronic theory. 2. Why atoms of inertgases do not form molecules? 3. Definechemical bond. How isitformed ? 4. Writea shortnote on ionicbonding. 5. Explainthe formationof MgO molecule. 6. What isa covalentbond ? How isitformed ? Writeproperties of covalentbonding. 7. Explainthe formation of (i)Cl, molecule, (ii)HCI molecule, (iii) Co, molecule,(iv)N molecule. 8. Distinguish between ionic and covalent bonds. 9. Define'covalent bond.Explain the fornmationof 'dative bond' giving example. 10.Write properties of co-ordinatebond. 11. Discuss hydrogen bonding and explainwhy molecule with hydrogen bonding has polar character. 12.Explaininterand intra molecularhydrogen bonding with suitable examples. 13.How is hydrogen bonding classified ? Give example of each class.Write characteristics of hydrogen bond. 14.Which bond occurswithinmetallic elements. Writeits characteristics. 15.Compare ionic,covalentand metallicbonds. 16.Explainany four metallic propertieson the basisof metallic bond. 17.What is Van der Waal'sforce ? Name itstypes.Write characteristics of Van der Waal's forces. 18."Arrangementof particlesimpartsolid, liquidand gaseous stateto matter". Explain inbrier. 19.Compare propertiesof solids, liquids and gases.