Question
Question: A mineral having the formula AB2, crystallises in the cubic close - packed lattice, with the A atoms...
A mineral having the formula AB2, crystallises in the cubic close - packed lattice, with the A atoms occupying the lattice points. The co-ordination number of the A atoms, that of B atoms and the fraction of the tetrahedral sites occupied by B atoms are
A
8, 4, 100%
B
2, 6, 75%
C
3, 1, 25%
D
6, 6, 50%
Answer
2, 6, 75%
Explanation
Solution
It is fluorite (CaF2) structure. Since formula is AB2
̃ No. of B atoms is twice the no. of A atoms. Hence B occupies all the tetrahedral voids (100%).
AB2 is (8 : 4) compound (Fluorite Structure Compound)
¯ ¯
C.N. of A C.N. of B.