Na and Mg crystallise in body-centered cubic and face-centered cubic crystals respectively, then the number of atoms of Na and Mg present in the unit cell of their respective crystals is :
Correct answer: D. 2 and 4
- A. 4 and 2
- B. 9 and 14
- C. 14 and 9
- D. 2 and 4
Explanation
The correct option is D (2 and 4 ) The body centered cubic cell consistes of 8 atoms at the corners and one atom at the centre. ∴n = (8/8)+1= 2. The face centered cell consists of 8 atoms at the eight corners and one atom at each of the six faces. This atom at the faces is shared by two unit cells. ∴n = 8/8 + (6/2) = 4
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A crystal lattice is the regular three-dimensional arrangement of particles in a crystalline solid. The content includes lattice points, unit cells, coordination number, packing patterns, and the differences among ionic, metallic, molecular and covalent network crystals, which should not be confused with amorphous solids.
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