Unit cell close packed structure (Void) and formula of compounds

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   Unit cell close packed structure (Void) and formula of compounds

1. What is meant by the term ‘coordination number’? What is the coordination number in-

 i)   square close packed structure in two dimensions   

(ii)   hcp 

(iii) ccp

2. AB AB arrangement has .............symmetry.

3.ABC ABC packing has     ............. symmetry 

4. The total number of tetrahedral voids in the face centered unit cell is ____________. 

5. How many number of an atoms in each of the following type of cubic lattices? 

            (i). Primitive (ii). face centred (iii) . Body centred.  iv)  hcp  and  (v ) ccp

 6.  A cubic solid is made of two elements P & Q. Atoms P  are at the corners of the cube & Q at the edge Centre & the body Centre. what is the formula                  of compound?                                                             

           ans-PQ4

7. A solid between A & B has the following arrangement of atoms. 

          (i). Atoms A are arranged in ccp array. 

           ii). atoms B occupy all the octahedral voids & half the tetrahedral voids

what is the formula of the compound?                                                                                  ans - AB2

8. In the corundum, oxide ions are arranged in h. c.p. array and  the aluminium ions occupy two thirds of octahedral voids. what is the chemical formula of corundum?               ans - Al2O3

9. In a crystalline solid, having formula AB2O4, oxide ions are arranged in a cubic close packed lattice while cations A are present in tetrahedral voids & cations B are present in octahedral voids. 

              I). what percentage of the tetrahedral raids is occupied by A? 

              ii). what percentage of the octahedral voids is occupied by B?                 

    Ans - i)12.5% ii) 50%

10. In a solid, oxide ions are arranged in ccp. cations A occupy one sixth of the tetrahedral voids cations B occupy one third of the octahedral voids what is formula of compound?                                                                                                                        ans-ABO3

11.  A compound is formed by two elements X & Y. Atoms of the element Y (as anions) make ccp and those of the element X (as cations) occupy all the octahedral voids. what is the formula of the compound?                                                         ans -XY

12. Atoms of element B form hcp lattice & those of the element A occupy 2/3rd of   tetrahedral voids. what is the formula of the compound formed by the element A & B?                                                                                                                                         ans - A4B3 

13.A compound is formed by two elements M and N the element N forms ccp & atoms of M occupy 1/3 rd of tetrahedral voids what is the formula of the compound.             

         ans- M2N3