The ZnS zinc blende structure is cubic. The unit cell may be described as a face-centered sulfide ion sublattice with zinc ions in the centers of alternating minicubes made by partitioning the main cube into 8 equal parts

(a) How many nearest neighbors does each `Zn^(2+)` have ?
(b) How many nearest neighbors does each `S^(2-)` have?
(c) what angle is made by the line connecting any `Zn^(2+)` to any two of its nearest neighbors ?
(d) What minimum `r_(+)//r_(-)` ratio is needed to avoid anion -anion contact, if closest cation-anion pairs are assumed to touch ?

Answer

A, C, D

Explanation

(a) As each `Zn^(2+)` ion is present in tetrahedral void, So it is coordination number is = 4
(b) Similarly `S^(2-)` ion have coordination number = 4
(c) As `Zn^(2+)` ion is present in tetrahedral void that's why line's connecting any two nearest neighbour and `Zn^(2+)` have angle `= 109^(@)28`
(d) For tetrahedral voids radius ratio is `(r_(Zn^(2+)))/(r_(S^(2-))) = 0.225`