Question

Predict the coordination number of Ca2+ in CaO crystal and also its crystal

structure. [​

Answer 1

The coordination geometry of divalent calcium ions has been investigated by analyses of the crystal structures of small molecules containing this cation of the molecules.

In order to determine structure of a crystal we have to apply radius ratio rule as follows.

Structure of CaO is like NaCl structure, Where Face cantered cubic(FCC) arrangement of

O2- ion with interpenetrating FCC lattice of Ca2+ ions.

So, Co-ordination number of Ca2+ ion is =6.