How will you distinguish between the following pairs of terms: (i) Hexagonal close-packing and cubic close-packing? (ii) Crystal lattice and unit cell? (iii) Tetrahedral void and octahedral void?
Answers
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Answer :
(i) Hexagonal close packing : In this type of packing, the second row of spheres is placed in the depressions of first row, third row is vertically aligned with first, fourth with second forming a pattern AB.AB ...
Cubic close packing : In this type of packing, the second row of spheres is placed in the depressions of 1st row of spheres is placed in depressions of second row, 4th row is vertically aligned with first, 5th with 2nd, 6th with 3rd forming a pattern ABC.ABC ...
(ii) Crystal lattice : Crystal lattice is a regular three-dimensional arrangement of atoms, ions or molecules.
Unit cell : Unit cell is a portion of crystal lattice which, on repetition, leads to the formation of crystal structure.
(iii) Tetrahedral void : The void between three spheres in direct contact capped by fourth sphere is called tetrahedral void. The coordination number of tetrahedral void is 4.
Octahedral void : Th void between three spheres in direct contact capped by three more spheres in direct contact is called octahedral void. The coordination number of octahedral void is 6.
Answer:
Explanation:
Hexagonal is ABAB.......
Cubic close packed ABCABC.......
Tetrahedral is coordinate is 4 and octahedral is 6.