types of lattice defects

In in ionic crystal of the type A + B - , equal number of anions and cations are missing from the lattice sites so that electrical neutrality is maintained it is called schottky defect. fig 2.29 - Schottky defect..

Born Haber Cycle helps us to calculate the lattice energy of ionic solid, provided other thermodynamic data is known. For example, the lattice energy of magnesium fluoride (MgF 2 ) can be calculated when the sublimation energy (S) of Mg = 146.4 kJ mol - 1 ; IE 1 and IE 2 val..

The defect, which arises due to the irregularity in the arrangement of atoms or ions are called point defects. Point defects are of three types: Stoichiometric defects Non-stoichiometric defects Impurity defects..

This type of defect is shown by highly ionic compounds which have High coordination number Cations and anions of similar sizes Examples: KCl, NaCl, KBr and Cs..

Stoichiometric Defects - If imperfections in the crystal are such that the ratio between the anions and cations remain same as represented by the molecular formula, the defect is called a stoichiometric defect. There are three types of stoichiometric def..

Defects in Crystals - According to third law of thermodynamic it is only at OK that true crystals passes perfect order of arrangement of atoms in pure crystals. But with rise in temperature some derivations from complete order takes place. Presence of impurities also adds to disorder. "An..

Non-stoichiometric Defects - If an imperfection causes the ratio of cations to anions to become different from that indicated by the ideal chemical formula, the defect is called non-stoichiometric. There are three types: Metal excess Metal deficiency Impurity defe..

Refraction of Light..

Group 13 elements such as Ga and Al and group 15 elements such as P and As can enter the crystal structure of group 14 elements Ge or Si substitutionally. Group 15 elements have one excess valence electron as compared to Group 14 elements (Si or Ge). Therefore after forming four covalent bonds, on..

fig 2.34 - Metal deficiency defect due to missing of a cation of lower valency and presence of a cation of higher valency Occurs when metals show variable valency. Example: Transition elements It occurs due to the missing of a cation from its lattice site and presence of th..