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Substances like iron, cobalt (Ferromagnetic) can make better permanent magnets because in the solid state these substances are grouped together in small regions called domains. Each domain acts like a tiny magnet. They are randomly arranged when placed in the unmagnetised state. But when they are placed in magnetic field domains align in direction of the magnetic field. But in case of...
The 14 group elements have four valence electrons, whereas group 15 elements like P have 5 valence electrons. In this, 4 out of 5 are used in making a bond with group 14 element and 1 is extra and becomes delocalised. This result in extra conductivity. So group 14 elements are required to be doped with the group 15 elements for forming n-type conductors.

1.22.  Ionic solids, which have anionic vacancies due to metal excess defect, develop colour. Explain with the help of a suitable example.

In impurity defect, the higher valency cation replaces the lower valency cation. An important point to be noted is that electrical neutrality is maintained. For e.g. In case of NaCl and SrCl2 , some of the sites of Na+ ions are occupied by Sr2+ . Two Na+ ions are replaced by Sr+2 ions. It occupies the site of one ion and the other site remains vacant. The cationic vacancies thus produced are...
AgBr shows both, Frenkel as well as Schottky defects.
ZnS shows Frenkel defect because there is a large difference in the size of Zn and S.
When a solid is heated some of the atoms moves out due to increase in its thermal energy. This leads to a vacancy defect. Affected physical property:- Since some of the atoms moved out so its density decreases.
We know that :                             We are given :         and                         and                         So we need to find z (no. of atoms present in unit cell) by putting all values in formula of density.  We get,                          . It is known that face centred cubic also has 4 atoms in its unit cell, So given cubic unit cell is face centred.
(i) Simple cubic:-  In a simple cubic lattice the atoms are located only on the corners of the cube.                               Thus, the edge length or side of the cube ‘a’, and the radius of each particle, r are related as a = 2r                               Volume of cubic unit cell =  =                              And  Volume of 1 atom :                                                 ...
It is given that element N forms CCP. Let us assume, the number of atoms of element N (which forms ccp) is x. Then no. of tetrahedral voids = 2x. It is also given that M occupies   of tetrahedral voids. So the number of atoms of element M :              So the molecular formula bocomes : 23.
Amount of compound given = 0.5 mol We know that,                                                                                                             So, No. of atoms     We also know that, No. of tetrahedral voids =   2(No. of atoms in closed packing)                                                                                                              No. of octahedral voids =...
In two dimensional square closed packed layer, one atom is in contact with 4 of its neighbouring atoms. So its cordination number is 4.  
(i) At corner:-    Each atom at a corner is shared between eight adjacent unit cells, four unit cells in the same layer and four unit cells of the upper (or lower) layer. Therefore, only of an atom (or molecule or ion) actually belongs to a particular unit cell.  (ii) At body centre of cubic cell:-   Since body centre atom completely belongs to the unit cell in which it is present, thus it is...