A hypothetical AX type of ceramic material is known to have a density of 3.55 g/cm3 and a unit cell of cubic symmetry with a cell edge length of 0.39 nm. The atomic weights of the A and X elements are 90.5 and 37.3 g/mol, respectively. On the basis of this information, which one of the following crystal structures is possible for this material?a) fluoriteb) zinc blendc) cesium chloride

Explanation:

For AX type ceramic material, the number of formula per unit cells is as follows.

or,    

where,   n' = no. of formula units per cell

            = molecular weight of cation = 90.5 g/mol

            = molecular weight of anion = 37.3 g/mol

          = volume of cubic cell = 3.55

           a = edge length of unit cell =

        = Avogadro's number =

          = density = 3.55

Now, putting the given values into the above formula as follows.

                      =

                     = 0.9

                    = 1 (approx)

Therefore, we can conclude that out of the given options crystal structure of cesium chloride is possible for this material.

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.