Ncert Solutions Chemistry Class 12th

1.13   (i) An atom located at the corner of a cubic unit cell is shared by eight adjacent unit cells. Therefore, 1/8th portion of the atom is shared by one unit cell.
(ii) An atom located at the body centre of a cubic unit cell is not shared by its neighbouring unit cell. Therefore, the atom belongs only to the unit cell in which it is present i.e., its contribution to the unit cell is 1

1.12 

(ii) Face-centered unit cell: In a face-centered unit cell, the constituent particles are present at the corners 
and one at the centre of each face.
End-centered unit cell: An end-centered unit cell contains particles at the corners and one at the centre of 
any two opposite faces.

1.11 The six parameters that characterize a unit cell are as follows.
(i) Its dimensions along the three edges, a, b, and c these edges may or may not be equal.
(ii) Angles between the edges these are the angles (between edges b and c), (between edges a and c), and (between edges a and b)

1.10 The significance of a lattice point is that each lattice point represents one constituent particle of a solid which may be an atom, a molecule (group of atom), or an ion.

1.9 Metallic solids are electrical conductors, malleable, and ductile.

1.8 In solid state, ions are held together by strong electrostatic forces and are not free to move about within the solid. In ionic compounds, electricity is conducted by ions. Hence, in molten state or in solution form, the ions are free to move and can conduct electricity

1.7 The given properties are the resource of a covalent or network solid. Therefore, the given solid is a covalent or network solid. Examples of such solid are quartz (SiO) and diamond (C).

1.5 As isotropic solid has the same value of physical properties when measured along different directions. Therefore, the given solid, having the same value of refractive index along all directions, is isotropic in nature. Hence, the solid is and amorphous solid. When an amorphous solid is cut with a sharp edged tool, it cuts into two pieces with irregular surfaces

1.4 Glass is basically an amorphous solid. When glass is made the silica is cooled from its liquid state, and it does not solidifies even when the temperature is dropped below freezing point. Hence, glass is a super cooled liquid. Due to this fluidity property, glass can be considered as a liquid of extremely high viscosity. The evidence of the fact can be seen in the windows getting thicker at bottom over a period of time.