 Now, in this we have two types of structure possible, in the final way we have two types of structure. The first one is normal spinal structure, write down, normal spinal, see all these are memory based, but they ask question on this, you cannot believe all these things, normal spinal structure, write down, in this structure O2 minus O charges 2 in this one, O2 minus O2 minus forms FCC packing, this information is very important, O2 minus FCC next slide, divalent A plus 2 write down, A plus 2 ion occupy 1 by 8th of tetrahedral void, 1 by 8th of tetrahedral void and half of octahedral void and half of octahedral voids are occupied by B3 plus ion or trivalent ion. Now, you tell me how many O2 minus ion are present, number of O2 minus ion depending upon that information, O2 minus what are you doing, O2 minus where is present? FCC, FCC, FCC right, FCC is O2 minus what will happen, O2 minus, okay, number of A plus 2, A plus 2 where is present? 1 by 8th of tetrahedral void, 1 by 8th of tetrahedral void, how many tetrahedral voids are there, 8th of 8th of 1 by 8th, so 8 2 plus, what about B3 plus, half of octahedral, so octahedral of 4, 4 into 1 by 2, so 2, though we again A B2 O4, A B2 O4, structure is A B2, okay, now if the question forms like this that in normal spinal structure, we remove all the atoms present in the void diagonal, okay, you should know that B3 plus octahedral are present, 8th octahedral are present, at the veto you can say how many B3 plus trivalent cations are there or trivalent cations are there, okay, so this information you should know, at least once you know this three, you can do all those things, okay, next example of this you write down, 7A2O4, MZ2O4, MZ2O4, MZ2O4, ZNFE2O4, okay, one question they haven't asked till date in this, if I ask you the ratio of what, ZNFE2O4, the ratio of tetrahedral void and octahedral void which are occupied, what is the answer in this, number of TVs and OVs which are occupied, how many TVs are occupied, 1A2 plus H, only 1 TV occupied, so 1 TV occupied, how many OV occupied, 2, so answer is 1, 2, 3, 4, 6, 5, okay, other way the code TV by OV unoccupied, how many TVs, TV store was occupied, 7 is unoccupied, right, so 7 divided by 2, 4 is 2 occupied, okay, next one, inverse spinal structure, normal spinal then inverse spinal structure, write down again, O2 minus CCP, okay, next time, divalent cation, sorry, divalent cation are occupied by 1 by 8th of tetrahedral void, okay, 1 by 8th of tetrahedral void, trivalent phase there is a difference, V3 plus may, 1 by 8th of TV occupied, plus 1 by 4th of OVV occupied, okay, 1 by 8th of tetrahedral void is occupied by trivalent cation and 1 by 4th of octahedral void is also occupied by trivalent cation, okay, so how many trivalent cation will be there, 1 by 8th of TV is 1, 1 by 4 of TV is 1, number of tetrahedral void, A2 plus what will happen, 1 by 8th of TV, A1, so it is 1 O2 minus 4th of FCC formula is AB O2, semi formula, right, AB2 O2, okay, AB2 O4, now H is our, you know all this, that overall if you see 1 tetrahedral void is occupied by trivalent cation and 1 tetrahedral void is occupied by trivalent cation, means what, equal percentage of tetrahedral void is occupied by both trivalent and trivalent cation, means they can give you options like this, so you should know this, 1 tetrahedral void, trivalent, what is trivalent void, divalent, apart from trivalent 1 octahedral void is also occupied by the trivalent cation, okay, inverse and spineless functions, any trivalent, okay, now what is the ratio of TV by OV occupied in this, how many TV is occupied, how many TV is occupied, AB3 plus in TV made or AB2 plus in TV made, so though occupies are right, 2 TV and how many OV, only 1, right, 2 by 1, all occupied out of 8, 2 are, so we have 6 and 3, so again 2 is 2, next slide down, corundum structure, the last one, corundum, L2 O3 type, A2 O3 simply, right, A2 O3 type structure, like we have A2 O3 examples, we can also have F E2 O3, all these are corundum structures, right on into this, O2 minus forms HCP arrangement, forms HCP arrangement and 2 third of the tetrahedral void are occupied by 2 third of the tetrahedral void are occupied by trivalent cation, A3 plus, trivalent cation is A3 plus, number of O2 minus is what, number of O2 minus, what 1 1, 1 by 6 is 6, HCP made, we have 1 2 3 4 5 6, 1 2 3 5 6, so we have 12 corundums and the distribution is what, among 6, this is structurally, and it is 1 2 3 in this plane and 3 is 2 per unit, so quadrant item contribution is 1 by 6, okay, so 12 by, so 12 into 1 by 6, 2 into 1 by 2 or D here, okay, so if we ask you, number of TVs, what will happen, N was TV, 2 N, FCC, we have 8 tetrahedral void, okay, so FCC does that effective at 4, so we have 2 into 4 8, why so happen, number of, can you work with me, number effective at M is N, then the number of tetrahedral void will be 2 N, and number of octahedral void will be N, it is not only for cubic, okay, so number of TVs will be 12, number of OVs will be 6, number of O2 minus, what will be 6, because N simply form, right, A3 plus, 2 third of tetrahedral void, so 2 by 3 of TVs, right, so A8 O6, A4, 2 third of octahedral void, or TVs, corundum, 2 third of octahedral void, it is not tetrahedral, I say tetrahedral, okay, so it is octahedral, it is not tetrahedral, okay, change this, so it should be 6, A over, and then it is A4 A2, okay, A4 O3 if it is there, then the molecule is not neutral, you can check, okay, so that is also one idea, okay, now in this one, there are 2-3 structures we have into this, like 2-3 different oxides, we have corundum structure, I have given you the example of this, like you have written Fe2 O3, right, so it is oxides of iron, Fe2 O3, as this structure CR2 also, O3 has this kind of structure, okay, so now in this we write down the first one, the structure of oxides of iron, in this only, corundum we are looking at this, structure of oxides of iron, the last one for this, the first one we write down FeO, the structure of FeO, FeO write down O2-O2- forms CCP packing, forms CCP packing, and Fe2 plus occupy all octahedral point, okay, next one, this lattice is similar to rock salt lattice, NaCl, rock salt lattice NaCl, it is a non stoichiometry compound, and some of the Fe2 plus ions in octahedral void, some of the Fe2 plus ions in octahedral voids are replaced by Fe3 plus ion, Fe2 plus replaced by Fe3 plus ion to maintain electrical neutrality, okay, so if one Fe3 plus ion is replacing the Fe2 plus ion, so to maintain electrical neutrality is what, three, see we have this, we have Fe3 plus, Fe3 plus replaced Fe2 plus, to maintain electrical neutrality is what the charge must be same, it is getting exchanged, right, so two Fe3 plus replace how many Fe2 plus ions, three Fe2 plus, to maintain electrical neutrality what we can say, two Fe3 plus ion replace three Fe2 plus ion, okay, the, see the structure is similar to that we have rock salt structure, but it is a non stoichiometry compound, the actual formula is Fe0.95O, this is the formula here, non stoichiometry, so like you see here it is not one, oxygen is one, this is not electrical neutrality, to maintain this electrical neutrality this exchange takes place, some of the Fe2 plus ion is replaced by Fe3 plus to maintain the neutrality, okay, this is one thing, not that important, next one we write down here, a structure of Fe2O3, Fe2O3, it is similar to the corundum structure, which has O2 minus HCP that is an Fe3 plus two third of octahedral point, okay, similar to that, Fe3O4 the next one we have all, I am not doing this one now, Fe3O4 we have already discussed this, okay, it is spiral structure, FeO dot Fe2O3, so O2 minus and Fe2 plus and Fe3 plus, trivalent and divalent where tell me here, okay, so it has similar that spiral structure tells me here, okay.