Question

Cesium chloride crystallizes in cubic unit cell with Cl- ions at the corners and a Cs+ ion in the centre of the cube. How many CsCl molecules are there in the unit cell?

Answer 1

Explanation:

This is obvious if we compare the CsCl unit cell with the simple cubic unit cell showing the interstitial site. We may also consider the neighborhood in which each ion finds itself. Each Cs+ is surrounded by 8 Cl- (so the Cs+ coordination number is 8) at the corners of each cube.