Question

A mineral having the formula, $A{B}_2$ crystallizes in the ccp lattice with A atoms occupying the lattice points. Select the correct statement(s).

• A. The co-ordination number of A is $8$.
• B. The co-ordination number of B is $4$.
• C. $100\%$ of the tetrahedral voids are occupied by B atoms.
• D. $50\%$ of the tetrahedral voids are occupied by B atoms.

Answer 1

Answer: (A), (B), (C)

The correct options are
A The co-ordination number of A is $8$.
B The co-ordination number of B is $4$.
C $100\%$ of the tetrahedral voids are occupied by B atoms.

As given,
Number of atoms = 4 (for ccp crystal)
Formula =$4A{B}_2=A_4{B}_8$
$\therefore$ CN of A=8 [CN of A =Number of Batoms]
CN of B =4 [CN of B=Number of Aatoms]
In ccp arrangement, all Tetrahedral Voids are occupied (fluorite type structure).