 chemical bonding the another chapter of of inorganic chemistry okay after this I'll go to the black and black history or tell me what do you know about a chemical bond what all things do you know what is the chemical bond first of all how do you define a chemical bond atoms forms chemical bond okay does all atom forms chemical bond no what all atoms we have it does not form chemical bond noble gases all noble gases what is the purpose why atoms form chemical bond to get stability okay to get stability and what is the reason of stability what is the thing that is atom is looking for and in order to achieve that it makes bond octet octet is the factor right any other factor of idea you have basically yes low energy state so basically yes your answer is correct that atoms have tendency to form bond in order to gain stability right octet is one of the way by which atom has tendency atom you know try to gain stability to attain octet what is octet all atoms tries to have 8 electron in their variance shell that is we call it as octet rule okay but octet rule is not the only thing for an atom to gain stability okay it is just one small theory in fact most of the atom does not follow octet there are only few atoms which follows octet rule okay so obviously octet is not the only reason there are other things also which will discuss in this chapter okay so first of all when atoms tries to form a bond okay so there must be some condition which makes the atoms which allows the atom to form a bond like for example if I consider oxygen right in the atmosphere oxygen exist as an atom or as a molecule right oxygen exist as O2 molecule right diatomic molecule nitrogen exist as again diatomic molecule that is N2 right phosphorus exist as tetratomic p4 molecule sulfur exist as exist as S8 molecule right but you see both oxygen and sulfur belongs to the same group nitrogen phosphorus belongs to the same group but their bonding ability is not same one forms diatomic molecule other one forms polyatomic molecule if you look at the structure in case of nitrogen it has N triple bond N structure oxygen also we have O double bond O with two lone pair on the oxygen atom phosphorus is tetrahedral geometry the four phosphorus atom plays at the corner like this just phosphorus right sulfur exist as like this it is we got this crown like the structure crown structure looks like a crown the point is why certain atoms forms multiple bonds when I say multiple bonds means double or triple bond why phosphorus is not able to form a double bond why sulfur is not able to form a double bond like oxygen or like nitrogen so there must be some you know reason behind this reaction condition we have all these things we can understand here in this chapter but here certain things you will study in organic chemistry also when you do P block elements there also will discuss but yes you will have an idea of all these things in this chapter that is okay how sigma bond forms how pi bond forms why phosphorus is not able to make a pi bond why sulfur is not able to make a pi bond right all these things you will understand right first of all we understand what are the different types of bond we have correct and then we'll go into the theory of these bonds okay what are the different theories by which the atom forms so what are the different types of bond first of all covalent ionic any other covalent ionic coordinate see first of all the bonds are classified into two categories two main categories okay you must you must have not done all these things types of bond you write down two types of bond we have the first type is the first type is interatomic bond what do you understand by this term interatomic bond between atoms right bond between atoms okay so this is basically interatomic bonds the term itself suggests these are the bonds between atoms interatomic bonds further it is classified in two following categories ionic bond covalent bond we have coordinate bond and metallic bond these are the bonds here mainly we'll discuss these three in this chapter metallic bonds are the bonds between the metal ions and electrons okay we are the interatomic bond similarly we have intermolecular bonds also bonds between the molecules okay right on bonds between the molecules oh yes intermolecular bonds this is nothing but the bond between the molecules for example we have end of all forces force of attraction second one is second one is hydrogen bond hydrogen bond also we have two types the first one is intermolecular hydrogen bond second one is intramolecular intermolecular and intramolecular hydrogen bond intermolecular between the two molecules intramolecular between the same molecule one by one we'll discuss all these bonds the first one you write down ionic bond ionic bond we also call it as electrovalent bond what is electrovalent bond right down it is actually a force of attraction attraction between cation and an anion between the cation and anion it is non-directional also it is non-directional and these are the bond forms between the atoms opposite nature opposite nature by complete exchange of electron exchange of electron for example you see we have an NaCl how NaCl forms Na loses one electron forms Na plus two eight one dielectronic configuration is and once it loses one electron it configuration is 2,8 so it gains its octet one electron goes out so sodium is also happy in this state because it has its octet complete on the other hand the chlorine takes one electron and converts into cl minus it is 287 it requires one electron 288 so chlorine is also happy both has its octet complete so when this Na plus and Cl minus comes close right we'll have an electrostatic force of attraction force of attraction which we call it as which we call it as ionic bond or electrovalent so it is just an electrostatic force of attraction between the positive charge ion and the negative charge ion that is cation or anion this is the ionic bond now one more thing you see here in detail if you go basic thing is that only when sodium loses its electron so for that we require ionization energy i.e. one when chlorine accepts one electron it requires electron affinity and it converts into Cl minus okay and then Na plus Cl minus combines it converts into NaCl and Cl minus NaCl so this is the removal of lattice energy it forms NaCl lattice and hence the lattice energy comes out so what all energies are involved into this ionization energy involved electron affinity involved and lattice energy involved okay ionization energy you have to provide in it is nothing but electron gain in enthalpy also you can say chlorine takes this electron converts into Cl minus and this is the removal of lattice energy when NaCl lattice forms some amount of energy comes out okay so overall what we can write here all these energies are involved in the formation of formation of NaCl lattice what why or because bond formation is always exothermic molecules atoms are going towards the stable state so obviously it has to go towards the lesser energies some amount of energy comes out so your doubt was electron gain in enthalpy also no it is the amount of energy releases when an electron is added to an isolated gases that is added or what exactly your doubt is in electron gain in enthalpy tell me more negative or more positive negative means energy releases okay positive means energy is getting consumed more negative that that is what the meaning of the negative and positive sign negative means energy releases positive means energy consumes right so more negative means more amount of energy releases like minus 10 and minus 12 if you compare so minus 12 is more negative than minus 10 both minus 10 and minus 12 it represents that 10 kilo joule of energy releases and 12 kilo joule of energy releases yes that's what negative and positive sign means nothing much these are the energies involved into this okay one more thing you must take care of the natural you know state of sodium is solid means sodium exists in solid state and we are providing ionization energy you see the ionization energy is defined only for gaseous atom so in this gaseous atom we can provide ionization energy one then it converts into NA plus gas and one electron goes out first of all to for this you must need to convert this solid into gas so for that we require the enthalpy of sublimation enthalpy of sublimation plus ionization energy and watching this okay chlorine the natural state of chlorine is gas only one electron you are adding so it is electron gain enthalpy of it or electron affinity and CL minus all these energy if you add you will get the enthalpy of formation so Delta H F for NA CL we can write enthalpy of sublimation plus ionization energy plus we require electron affinity right minus we require lattice energy because lattice energy comes out so from this you if you know the enthalpy of formation you can find out the lattice energy of any substance this is the indirect method to find out the lattice energy of any substance once again now since ionization energy and electron gain enthalpy is involved into this electron affinity is involved into this okay then which element can easily form ionic bond for that the condition we have right now favorable condition for the formation of ionic bond for the formation of ionic bond that is low ionization energy low ionization energy next what we can write high electron affinity high electron affinity and high lattice energy more energy releases more stability the compound will get whatever the value of E a electron affinity it will be positive or negative will write down with the sign okay lattice energy comes out so we'll take it as negative yes Pradyumna understood so this is the condition required now what you have to you know keep in mind is higher the electronegative see what happens here one atom is raising electron and other one is getting electron right so other one should have should be more electronegative and the first one should have less electronegative that's why the is this kind of bond forms between the atoms of opposite nature one is electropositive other one is electronegative so mainly this is the bond forms between metals and non metals metals when combines with non metals it forms ionic bond forms ionic bond okay so metal we can consider mainly g1 g2 elements of group one group two to some extent g3 also we consider g13 sorry boron family to some extent not much g1 g2 group one group two elements you can take group 13 also we can take to some extent non metals could be group 15 group 16 group 17 these are the non metals so the bond forms between the elements of these groups are mainly ionic bond there's a term called electro valency it is a number of electron gained or lost in forming a bond in forming a bond or lost in forming a bond so electro valency for elements of group one the electro valency is one for group two the electro valency is two for group 13 the electro valency is three maximum possible i know of this thing exchange of electron is this all these elements group of elements loses electrons these many electrons it can lost electron lost one two and three the electron negative elements group 15 16 and 17 this will gain electron like for example you'll see group 15 is nitrogen family can take three electrons group 16 is oxygen family can take two electrons and group 17 and have one electron this is the electro valency and electrons gained one note you write down higher the difference between higher the difference between the group number here the difference between the group number more will be the electronegativity difference and more will be the i need character in the bond higher is the difference between the group number more will be the electronegativity difference and more will be the i need character in the bond next right now see lattice energy because n a plus c l minus forms so it is it is a lattice that forms by the combination of n a plus and c l minus and when the lattice forms there are some amount of energy evolves in this process okay so how to find out the lattice energy of any lattice okay little bit i have discussed already right how to find out the lattice energy of any lattice so lattice energy there is no direct method to find out the lattice energy of any lattice but indirectly we can find it okay and we can find it indirectly by the method called bond haver cycle okay so write down the heading in this write down this is the indirect method to find out indirect method to find out the lattice energy of any lattice lattice energy of any lattice okay suppose we have this one we'll take an example of so n a c l only n a solid plus half of c l to gas converts into n a c l solid okay so first of all this n a we need to convert this into n a gas and then this converts into n a plus gas this chlorine also you need to convert this into chlorine atom and then this chlorine atom must convert into c l minus okay and when these two combines okay and when these two combines lattice energy comes out and forms n a c l okay so what are the energy involved here you see in the first one we have enthalpy of sublimation n a c l forms delta h of sublimation and then we have ionization energy here we have bond energy you need to break the chlorine chlorine bond since half mole we have so half of the bond energy you need to supply and then we have here the electron affinity of it lattice energy then it releases okay so the enthalpy of formation of this delta f of h this means enthalpy of formation of n a c l this is equals to the enthalpy of sublimation all these energy will add plus we'll have the ionization energy plus we'll have half of b e bond dissociation energy plus we'll have electron affinity whatever electron affinity negative main leaving it minus of e plus we'll have lattice energy releases minus of lattice energy this is the equation we have once this enthalpy of formation you have you can put all these value and you can find out the lattice energy all these values will be given in that question you don't have to calculate this bond energy b e is the bond energy of chlorine chlorine bond that you need to break yes c l 2 you need to convert into the atom that is chlorine enthalpy of sublimation for phase change solid to gas if you need to convert you need to provide that energy that energy is known as enthalpy of sublimation so this process this method we call it as enthalpy we call it as bond habit cycle okay everything will be given all the energy which is written here you cannot find out this energy so it will be given in that question okay however the thing is not that important okay they won't ask you these questions in the example next the properties of ionic compound right now first one right on physical state the molecule which has ionic bond physical state is mainly solid it has high melting point and boiling point these are bad conductor of electricity in solid state in solid state right on but in aqueous state they are good conductor aqueous state they are good conductor ionic bond is non-directed okay so these are the some properties of these compounds together next slide down covalent bond second type covalent bond it is formed by the sharing of electron it is the sharing of electrons and the sharing of electron takes place electron takes place in such a way in such a way that their octet is complete gets complete sorry octet gets complete so in order to complete their octet they've just shared electrons okay but in case of hydrogen the octet is not possible in bracket right on except hydrogen so if you look at this you know examples we have H2 molecule and this forms by the sharing of electrons of the two hydrogen atom 1 1 electrons right so each of the hydrogen atom remember this in the bonding state we consider the two electrons for both hydrogen like if I ask you how many electrons this hydrogen has in this bonding state your answer would be two how many electrons this hydrogen has your answer would be again so we'll we'll count the bonding electrons for the bonded atoms okay this electron for this one this electron for this one okay so we have two electrons here so we say that hydrogen molecule completes its duplet it's not octet but it is duplet if you consider HCl so in HCl the duplet of hydrogen is there but the octet of chlorine is there because chlorine has eight electrons hydrogen has only two electrons chlorine complete octet hydrogen is duplet in O2 we have double covalent bond O double bond O so we have double covalent bond and in N2 we have triple covalent triple covalent bond finished guys so this is for covalent bond next one is coordinate bond the third type is coordinate bond coordinate bond we also call it as dative bond coordinate bond or dative bond so what is coordinate bond you see right down these are the bonds in which these are the bonds in which the electron pair these are the bonds in which electron pair generates from generates from the same atom there are the bond forms when the electron pair involves in bonding generates from the same I explain this you see first of all a molecule we have NH3 in which the nitrogen has one lone pair of electron and electron pair accepted we have for example H plus so what happens in this when this comes closer to this the nitrogen donates its lone pair of electron into the vacant orbital of H plus and it converts into this H and a positive charge on nitrogen because it donates its electron pair so this bond that forms we call it as coordinate bond electron it originates from nitrogen only hydrogen has no electron H plus has no electron here but still it managed to make a bond with this nitrogen since it accepts the electron pair from the molecule which donates electron pair we call it as electron pair donor electron pair donor and this one is electron pair acceptor acceptor this is what the coordinate bond is okay so this arrow from donor to acceptor this arrow is the coordinate bond and this representation is the old methodology this is the old methodology nowadays we represent this coordinate bond in a different manner and we'll discuss that coordinate bond is the bond in which again I'm repeating the definition guys one second coordinate bond is the bond in which the electron pair right on like with the shared pair of electron originates from the same atom shared pair of electron originates from the same atom that is what happening here nitrogen donates its electron to H plus ion same atom is giving its electron hence the bond is coordinated yes fine okay like I said this is the old methodology the arrow representation nowadays we represent coordinate bond in a different fashion okay one note you write down first of all one note you write down knot is coordinate bond coordinate bond is considered as is considered as a type of covalent bond nowadays coordinate bond E.P. is the electron pair electron pair acceptor electron pair donor E.P. is the electron pair not on this point nowadays coordinate bond is considered as as a type of, a type of covalent bond. There are two cases to represent the coordinate bond. We have two cases, case one, as a type of covalent bond. If the elements, if the elements belongs to second period, belongs to second period. Okay, so in this case, what happens? Suppose we have a lone pair donor, an atom A, and B is the lone pair acceptor, or electron pair. Donor is A, and this one is electron pair acceptor. So in this case, when the both atom belongs to, when the donor atom belongs to second period, then what we assume first, that this donates one electron to this B, half arrow means only one electron, okay? Half arrow means only one electron, and then it converts into A with one electron, positive charge, because it donates one electron, and B with one electron, negative charge, right? And then we have the sharing of electron between the two, because both has one unpaired electron. A makes a bond with B by sharing of electron, positive and negative, this becomes the coordinate bond. So in this kind of thing, the coordinate bond is represented by a simple bond like this, simple single bond, this way. There's no arrow like this, like this it is represented, plus and minus. First it donates one electron, becomes one electron each on these ions we have, one on B, one on A, and then the sharing of electron between them, the sharing of electron, it gives you a coordinate bond. So this kind of, you know, we define the coordinate bond nowadays this way. So this is the coordinate bond right on here. Now if the donor elements belongs to third or higher period, case two. See the covalent bond, what happens in covalent bond? You just try to understand this with an example. First of all you see the coordinate bond. The thing is what the shared pair of electron in coordinate bond originates from the same atom, one single atom. Here nitrogen gives us electron and forms a bond with hydrogen. Here A is giving us electron and forms a bond with B. But in covalent bond, both atom give us electron and takes part in the bonding, like this one you see. Suppose you have HCl, right? In HCl we have one electron of hydrogen and then one electron of protein, but that is not happening in coordinate bond. Are you getting my point Anj? Yes, that is the difference between the coordinate bond and the covalent bond. Coordinate bond, the bond pair of electron originates from the same atom. Here both atom gives its electron and forms and shares its electron and forms a bond. That's the difference between the coordinate bond and covalent bond. But now coordinate bond is considered as a type of covalent bond. And that is how we define it. One electron A donates first to B. A B will have a negative charge, A will have a positive charge. When both ion has one electron, sharing takes place and forms a covalent bond, right? Now, in case two, if elements belongs to, third or a higher period, the coordinate bond is shown by a double bond. Like for example, SO3, sulphur trioxide. If you see the structure of this S double bond O, a coordinate bond with oxygen, again a coordinate bond with oxygen. But in the recent development, this coordinate bond is represented by a double bond like this and a double bond like this. Both are correct, but this is the current or the modern concept of it, double bond. This is not a double bond actually, it is a coordinate bond with sulphur trioxide. So this is the two cases we have. Suppose if you have NH3, some more examples we take. NH3 with one lone pair and one H+. So what happens, this NH3, give it one electron to this H+, because this is the second period element, one electron to this H+, and then we'll have here NH, H, H under electron, positive charge, and H won't have any charge with only one electron. Because it has positive charge, takes one electron, the positive charge goes off, and it has one electron. Now in this we say the sharing of electron takes place, and then H, both has one electron. So it converts into NH, positive charge on nitrogen, and this NH4. This is the coordinate bond. Did you understand this? Why this is required? Because we have observed that the molecules which has coordinate bond or the molecules which has coordinate bond, they have similar properties. Then they started thinking off that if the properties are similar, then maybe there will be some similarities in the bonding, right? And that's how they got to know this particular thing. No, in case of a triple, in case of a second period element, it is just a single bond, like it is I have shown in the NH4+. When case two it is there, when case two, see, this is the example of the first case. Case two is this, SO3. Third period element, a double bond. Next right now. Properties of the compound, right on the properties of the compound having covalent or coordinate bond, coordinate bond. First one is the physical state, physical state. In the physical state of these compounds, these components, compounds having these two type of bond, okay? The physical state of these bonds are mainly liquid or gas, physical state of these bonds are mainly liquid or gas, but some may exist in, but some may exist as soft solid, but some may exist as soft solid. Some may exist as soft solid. Mainly it is liquid or gas, but some may exist also. like for example you see molecules like I2 iodine, S8 P4 these are soft solid molecules like F2 Cl2 these are gases mainly BR2 is liquid all these things you must know keep that in mind and the state of this. This kind of compound generally has low melting point and boiling point melting point and boiling points are low but there are some compound exception you can consider as diamond or carburentum SIC is carburentum which has boiling point right which has melting point more than to that of ionic compound more than to that of ionic right now melting point is more right now these compounds are generally bad conductor of electricity of the compounds but some of the compounds may show may show conductive nature some of the compounds may show conductive nature may show conductive nature because of its polar nature because of its polar nature or self ionization because of its polar nature or self ionization for example water molecule H2O may get self ionized like this it converts into H3O plus and OH minus because of its ions it shows conductive behavior right graphite another exception here graphite also conducts electricity electricity because of free electrons so these are the general rules but there are some no exception we have fourth one dissolves in in non polar solvent because these compounds covalent compounds are non polar so non polar compounds dissolve in non polar solvent right polar compounds dissolve in polar solvents okay we know this rule by this we memorize this rule by this like dissolves like okay like dissolves like means polar dissolve in polar non polar dissolve in non polar okay covalent bond is directional in nature and is directional in nature and hence and hence shows isomerism and hence shows isomerism so in the molecule isomerism exists because of polar sorry because of covalent or coordinate bond these compounds are generally shows molecular reaction generally shows molecular reaction molecular reactions are those reactions in which some new bond forms and some old bond breaks and these reactions get over or get finished in finite time okay like in hour or two it's not like it takes months like rusting off very slow process not a molecular reaction right neutralization reaction acid base is extremely fast right not a molecular reaction those are ionic reactions neutralization reactions are ionic reactions okay slide down to the covalent compound covalent compound shows molecular reaction shows molecular reaction which involves bond dissociation and bond bond dissociation and bond formation which involves bond dissociation and bond formation it takes finite time for completion and it takes finite time for completion just a second okay I'm repeating myself covalent compound gives molecular reaction covalent compound gives molecular reaction which involves bond dissociation and bond formation which involves bond dissociation and bond formation and it takes finite time for the completion of reaction it takes finite time for the completion of reaction for example N2 plus 3 H2 gives 2 and H3 I'll repeat did it right guys I'll go to the previous slide and I'll repeat this one again see I said molecular reaction covalent compound gives molecular reaction which involves bond dissociation or bond formation and it takes finite time for the completion it takes finite time for the completion of reaction did it right all of you so these are the few properties of the compounds having covalent and coordinate bond and I think we have already discussed correct now we have theories of covalent bond like what all theories we have because of that the formation of covalent bond takes place okay we'll discuss that but before that we'll see what is octet rule we'll start this after the break okay we'll resume the session at 6 20