Given: Radius of cation Mg2+ (r+ ) = 65 pm
Radius of anion S2− (r− ) = 184 pm
To find: i. The coordination number of MgS = ?
ii. Structure of MgS = ?
Radius ratio = Radius of the cation/ Radius of the anion
Since the radius ratio lies in between 0.225 – 0.414
The coordination number of MgS is 4. And the structure of MgS is Tetrahedral.