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Question
In a compound, nitrogen atoms (N) make cubic close packed lattice and metal atoms (M) occupy one-third of the tetrahedral voids present. Determine the formula of the compound formed by M and N?
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Solution
In ccp, no. of atoms per unit cell = 4
Thus, of tetrahedral voids = 2 × No. of atoms in ccp = 2 × 4 = 8
Only one-third of tetrahedral voids are occupied by metal M.
No. of metal atoms, M = `1/3 xx 8`
M:N = `8/3`: 4 = 2:3
Thus, formula is M2N3.
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