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Metals such as copper and silver crystallize in this structure. Both these types of close packing are highly efficient and 74 % space in the crystal is filled. In either of them, each sphere is in contact with twelve spheres. Thus, the coordination number is 12 in either of these two structures.
Question: A compound is formed by two elements M and N. The element N forms ccp and atoms of M occupy 1 / 3rd of tetrahedral voids. What
is the formula of the compound?
Answer: The ccp lattice is made by the atoms of the element N.
Here, the Number of tetrahedral voids = 2 X number of particles of the elements N.
According to the question, the atoms of element M occupy = 1 / 3 rd of the tetrahedral voids.
Therefore, the number of atoms of M is equal to 2 x 1 / 3 = 2 / 3rd of the number of atoms of N. Therefore, the ratio M: N = 2 / 3: 1 = 2:3 Hence formula of the compound is M2N3.