The Solid State

In hexagonal close packed structure, there is 6 atoms per unit cell. Number of octahedral voids Number of tetrahedral voids Total number of voids Total number of voids per atom In mole compound the total number of voids In mole compound, the total number of voids

, on heating, loses oxygen and thus, the zinc metal becomes in excess in crystal. Hence, the formula of becomes The excess ions move to interstitial sites and the electrons to neighbouring interstitial sites. The electrons are responsible for the yellow colour of Thus, yellow colour of is due to metal excess defect

Let the number of atoms in cubic close packing be .
Number of tetrahedral voids
Since, forms cubic close packing, the number of atoms
occupy one third of tetrahedral voids, the number of atoms


Therefore, the formula of the compound is .

Number of atoms present at each corner

Number of atoms present at the centre of edges

Number of atoms present at the centre of cube
Formula of cube or

Radius ratio, }=0.524$
Therefore, ions prefer to occupy octahedral site .

Substances which show permanent magnetism even in the absence of the magnetic field are called ferromagnetic substances, e.g., and are ferromagnetic substances.

The constituent particles of amorphous solids have only short range order of arrangement, i.e. regular and periodical arrangement of particles is seen to a short distance only. The structures of amorphous solids are similar to that of liquids. Glass, rubber, plastics, etc., are some of the examples of amorphous solids. Amorphous solid are isotropic in nature, i.e. physical property of amorphous solid are same in all directions.