In cubic ZnS,the radii of the Znand S atoms are 0.83Ao  and 1.74 Ao respectively. What is the edge length of the unit cell of ZnS?

This figure shows one part of eight cubic components of a unit cell of ZnS.Let edge length of the unit cell = a3×a2×12=rZn2++rS2−or 3a4=0.83+1.74=2.57or a=2.57×43=5.935Å