Question

If $AgI$ crystallizes in zinc blende structure with $I^{-}$ ions at lattice points. What fraction of tetrahedral voids is occupied by $Ag^{+}$ ions?

• A. 0.25
• B. 0.5
• C. 1
• D. 0.75

Answer 1

Answer: (B)

0.5

Answer 2

In $AgI$ crystal, number of $Ag ^{+}$ions is equal to $I ^{-}$ions. However, the number of tetrahedral voids are twice the number of atoms forming the cubic lattice. $\therefore$ Number of tetrahedral voids occupied by $Ag ^{+}$ion $=50 \%$