Statement-I : Density of an ionic solid decreases due to Schottky defect.
Statement-II: Packing efficiency of ccp structure is 74%.
I) Frenkel defect is a dislocation defect. One of the ion(generally cation) leaves the lattice point and occupies the interstitial site but does not leave the crystal, thus no change in the density of crystal.
Schottky defect is a vacancy defect in which equal number of cations and anions will be missing the lattice points.It leads to decrease in density.
II) Packing efficiency of ccp structure is 74%.