Question

Schottky defect lowers the density of related solids. Explain.

Answer 1

In ionic crystals the regular crystal pattern gets disturbed by irradiation or by supplying a heat energy. As the structure gets disrupted it will be known as a defect. There were two types of defects namely the Frenkel and Schottky defect. In Schottky defect the ions will decrease and results in the decrease of mass leads to decrease in density.

Complete answer:
Crystallographic defects are interruption from the regular arrangement of atoms. These are different defects like stoichiometric defects and non-stoichiometric defects. Stoichiometric defects include vacancy defect, interstitial defects, Frenkel defect and Schottky defect.
In both the Frenkel defect and Schottky defect the ions will miss from the regular arrangement. Schottky defect occurs when heat energy is supplied to the crystal. The temperature will be increased which leads to the thermal vibration resulting in the creation of gaps in the crystal pattern. These gaps occurred due to the missing of both cations and anions.
Thus, the mass of the crystal will decrease. As the density is related to mass and volume where the density is directly proportional to mass. As the mass decreases in the Schottky defect the density also decreases.
Thus, the given statement is true.

Note:
Missing of both the cations and anions results in the decrease in the whole mass of the crystal. It leads to the decrease in density. Schottky defect occurs in the crystal formed by ions of similar size. One of the examples is potassium chloride where potassium and chlorine are of similar size.