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1.Define the term Enantiotropy?
                      The allotropic forms of a given element is stable at all temperatures below a certain temperature is called transition temperature, while the other form is stable above this temperature. The phenomenon is called enantiotropy.
2.Define Isomorphism?
           When two or more crystalline substance have the same number of atoms and the same shape.(ie; atoms in them are united in similar manner), the phenomenon is called isomorphism.
3.Define the term Isopolymorphism?
        When each of the two polymorphous forms of a substance is isomorphous with each of the two polymorphous forms of some other substance, the two substances are said to be isopolymorphous with each other and the phenomenon is called isopolymorphism.
4.What is an ideal crystal?
           An ionic crystal which has the same unit cell containing the same lattice points through out the whole of crystal is known as ideal crystal.
5.What do you mean by term imperfection or defects?
            Any deviation from completely ordered arrangement in the crystal.
6.Why defect in crystals are arise?
        (i) Defects in ionic crystals due to electrons.
        (ii) Missing of constituent particle creating a vacancy or hole in the crystal.
        (iii)When an atom or anion is displaced from its latice to interstitial space.
        (iv)Presence of impurity at lattice site or interstitial space.
7.How electronic imperfection takes place in solid state?
        At low temperature, the electrons in co-valent crystals (eg: si, Ge) are held tightly in the plane. When the temperature of the substance is increased, more and more electrons are exicted to higher energy level.These behave like free moving electron in the metal. Consequently, these substances start conducting and their conducting ability increases with increase in temperature. This type of conduction is known as intrinsic conduction. The above behaviour of electron at higher temperature is termed as electronic imperfection in solid state.
8.How atomic imperfection takes place?
          This defect arise due to the irregularity of arrangement of atoms or ions are called atomic imperfection. It is due to missing or misplaced ions called point defect.
9.What are the two types of points defect?
       (i) Defects in stochiometric defect
        (ii) Defects in non-stochiometric defect
10.What are the two types of stochioiometric defect?
                (a) Schottky defect
                (b) Frenkel defect

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