 Hello friends today in the session, we are going to discuss about the coordination compound actually the bonding in coordination compound Okay, so There are various theories which you know explains the bonding of coordination compound, right the theory we are going to discuss today is Valence bond theory Right valence bond theory Valence bond theory Which in short we also call it as VBT Right valence bond theory Okay See this theory is almost similar to the theory that we have discussed in Chemical bonding valence bond theory. We have also already those things are here Also that number of atomic orbital combines and gives equal number of hybrid orbital All those things are same even the postulates of this theory few points are very similar or same, right? Two three points we have difference here that we are going to discuss here Right this valence bond theory is given by Pauling, right and this theory This theory mainly deals with this theory It mainly deals with It mainly deals with the geometry geometry and magnetic properties right geometry and magnetic Property Of the complexes of the Complexes, okay So for geometry, we must know the hybridization of the complex, right Magnetic property means what whether it is Di-magnetic or paramagnetic that is what the magnetic property we have paramagnetic or Dmagnetic, so these two informations We will get with this valence bond theory, okay The main postulates of these theory are The important points of this theory are the first point You should know all these points because the you know the bonding and all we are going to discuss based on these postulates only okay, so So the first point here is the central metal atom the first point the Central metal atom CMA. This is the abbreviation. We are going to use for this term central metal atom The central metal atom Loses a required number of required number of electrons number of electrons to form iron to form iron And these numbers are nothing but the valency of The cation right so to form an iron which is generally a cation second postulate is what the second postulate is Depending upon the coordination number depending upon the coordination number the central metal atom coordination number the central metal atom CMA has equal number of equal number of vacant sp and d orbital sp and d orbitals which forms which forms hybrid which forms hybrid orbitals forms hybrid orbitals And the other thing is what the number of hybrid orbitals In this only a light down here the number of hybrid orbitals orbitals form Is equals to the number of atomic orbitals the number of atomic orbitals Combines Okay, the number of hybrid orbital forms is equals to the number of atomic orbital combines Okay third one is third one Is in case of strong ligand in case of strong ligand in case of strong ligand There may be there may be there may be rearrangement rearrangement of electrons in the atomic orbital in the atomic orbitals against the hunt's rule against the hunt's rule Against the hunt's rule hunt's rule rearrangement is also possible Okay, this is the next point Okay Next point is the fourth one the ligand attached with the central metal atom with coordinate bond coordinate bond has considerable amount amount of polarity as considerable amount of polarity fourth point is this and the fifth point if the complex if the complex contains unpaired electron unpaired electron then it is diamagnetic if all the electrons all the electrons are paired then diamagnetic diamagnetic Okay, so these are the postulates we have of valence bond theory The most important postulate is this one in case of strong ligand there may be rearrangement of electrons in the atomic orbitals against the hunt's rule Okay and this paramagnetic diamagnetic we already know and this thing is number of hybrid orbital forms right most important point is the third point now we'll see uh the explanation of this one more thing we should know here one more thing we should know is I'll draw a table here like uh the first thing is uh coordination number coordination number then second thing I'll write down here is geometry and the last one is hybridization hybridization coordination number can be two three four five and six these are the coordination number Okay, so we'll draw a table here Okay, if the coordination number is two then the geometry of the molecule is linear and hybridization is sp coordination number is three then it is trigonal planar trigonal planar and hybridization is sp two four it is either tetrahedral or square planar tetrahedral means sp3 hybridization square planar means dsp2 hybridization five it means trigonal bipyramidal trigonal bipyramidal or we can also have square pyramidal trigonal bipyramidal or square pyramidal sixth one is uh we can have a octahedral or square bipyramidal okay trigonal bipyramidal hybridization can be or dsp3 three or it can be sp3d this one it can be sp3 d2 or d2 sp3 any of these two hybridization is possible for these geometries okay few more things we should know here and that is a trigonal bipyramidal structure if you see it is uh this is a triangle okay so we'll have metal here in the center of this and this gives you this gives you one ligand here and one ligand here all these three corners we have ligand here we have ligand here we have ligand and here we have ligand okay so this one is nothing but the trigonal bipyramidal structure the base is a triangle and this forms a bipyramidal this this no even this also the three-dimensional figure so it's very difficult to you know show here in this thing we have here also here also right this is trigonal bipyramidal this structure is trigonal bipyramidal tbp triangle is the base and bipyramidal top and bottom it is trigonal bipyramidal structure okay in this what happens this is metal here here we have the metal and these are ligands okay all these are ligands attached to the metal correct so in this the three bond length three bond length are same and two bond length are different different means this bond length of ligand and metal this bond length this bond length different and these three bond lengths are same okay similarly when you consider square pyramidal or square bipyramidal first of all I will show you what is a square pyramidal square pyramidal is something like this right we have a square and on the center of it here is the metal we have and the corner of the square contains ligands this is ligand this is ligand this is ligand this is ligand I did all these ligands are bonded with the metal with coordination bond coordinate bond sorry with this coordinate bond pyramidal if you talk about square pyramidal the base is square and only one ligand is attached from the top or from the bottom like this one ligand is here right this is square square pyramidal right because these are you know this is the base is the square and this is actually a pyramid if you try to you know imagine this a geometry three-dimensional imagine if you do this forms a pyramid right square is the base and a pyramid it is a square pyramidal bipyramidal means what I'll explain here only what is bipyramidal one ligand is attached with the metal from the bottom of it like this this is the ligand we have right so now this ligand is also attached with the every corner of the square like this right so this is square bipyramidal right so in this the two bond length are different and four bond length are same bond length of bond length bond length of metal and ligand bond length of metal and ligand this information we must have okay now you see how to find out the geometry and you know the other magnetic properties of the metal okay so that we are going to discuss next