Question

Crystal defect indicated in the diagram below is
Na⁺ Cl⁻ Na⁺ Cl⁻ Na⁺ Cl⁻
$Cl^- \Box Cl^- Na^+ \Box Na^+$
$Na^+ Cl^- \Box Cl^- Na^+ Cl^-$
$Cl^- Na^+ Cl^- Na^+ \Box Na^+$
(a) Interstitial defect
(b) Schottky defect
(c) Frenkel defect
(d) Frenkel and Schottky defects

Answer 1

(b) Schottky Defect

because this defect occurs when oppositely charged atoms (cation and anion) leave their corresponding lattice sides and create a pair of vacancy defects. since both cation and anion delete the lattice sites at the same time so overall electrical neutrality of the crystal is maintained. Moreover schottky defects occur in ionic crystals where the size of anion is almost same with the size of cation.