Question

In solid lattice, the cation has left a lattice site and is located at an interstitial position, the lattice defect is:
(a) Interstitial defect
(b) vacancy defect
(c) Frenkel defect
(d) Schottky defect

Answer 1

Hint: In a solid crystal lattice, there might be some defects. These defects can be missing two or more electrons or an atom occupying an interstitial site by displacing from its actual site.

Complete step by step solution:
Some crystal lattices of solids have the same number of positive ions and same number of negative ions. Their ratios are exactly indicated by their chemical formulae. Such solids are called stoichiometric solids. Defects caused in such solids without changing its stoichiometry are called stoichiometric defects.

-There are two types of stoichiometric defects. One is schottky defect and the other is frenkel. Schottky defect occurs when equal numbers of cations and anions are missing from the lattice.

-Frenkel defect arises when an ion is missing from its actual lattice site and it occupies any interstitial site. The whole electrical neutrality of the solid is maintained because the number of cation and number of anions remains the same. This defect mainly occurs when there is a large difference in the size of cation and anion. This defect mainly occurs in compounds having low coordination numbers and the anion and cation has different sizes.

-Interstitial defects, where one or more atoms occupy an unoccupied site in a crystal structure. This takes place only in non-ionic solids, and this increases the density of substance.

-Vacancy defect is a point defect. It is a non-stoichiometric defect.
Thus, in a solid lattice, the cation has left a lattice site and is located at an interstitial position, the lattice defect is Frenkel defect. The correct option is (c).

Note: The answer might be confused with interstitial defect. Frenkel defect is stoichiometric defect and interstitial defect is non-stoichiometric defect.