Question

Predict the hole occupancy and coordination number of
cation in K2S, NH4Br, CoF2, TiF2

Answer 1

Compound              Cation            Structre     Void occupancy    Coordination No.

K₂S                           K⁺                       BCC             32%                  8

NH₄Br                  NH₄⁺                        FCC                 26%                   6

CoF₂                        Co⁺²                           HCP                 26% 12

TiF₂                    Ti⁺²                             HCP                 26%                  12

packing efficiency of sphere =[ No. of atoms in one unitcell (Z) * * 100 ] / Total volume of unitcell(a³)

hole occupancy =100 - sphere occupancy

For BCC Z = 2    a = 4r / 3^1/2

For FCC   Z = 4    a = 2*2^1/2 * r

For HCP   Z =6     vol of unitcell = 24* 2^1/2 * r³