Coordination Number in Ionic Structures

In ionic structures, the coordination number refers to the number of ions that surround a central ion in a crystal lattice. It represents the number of nearest neighbors of an ion in a solid.

The Coordination Number in Different Structures

Let's analyze the coordination numbers in the given structures:

a) Cesium chloride (CsCl)
In the CsCl crystal structure, each cesium ion (Cs+) is surrounded by 8 chloride ions (Cl-) and each chloride ion is surrounded by 8 cesium ions. Therefore, the coordination number of both ions in CsCl is 8.

b) Sodium chloride (NaCl)
Similarly, in the NaCl crystal structure, each sodium ion (Na+) is surrounded by 6 chloride ions (Cl-) and each chloride ion is surrounded by 6 sodium ions. Hence, the coordination number of both ions in NaCl is 6.

c) Zinc sulfide (ZnS)
In the zinc sulfide crystal structure, each zinc ion (Zn2+) is surrounded by 4 sulfide ions (S2-) and each sulfide ion is surrounded by 4 zinc ions. Thus, the coordination number of both ions in ZnS is 4.

d) Sodium oxide (Na2O)
In the sodium oxide crystal structure, each sodium ion (Na+) is surrounded by 6 oxygen ions (O2-) and each oxygen ion is surrounded by 6 sodium ions. As a result, the coordination number of both ions in Na2O is 6.

Conclusion

Based on the analysis, the coordination numbers of both ions are the same in cesium chloride (CsCl), sodium chloride (NaCl), and zinc sulfide (ZnS). These structures have a coordination number of 8, 6, and 4, respectively, for both ions. However, in sodium oxide (Na2O), the coordination number of sodium ions is 6, while the coordination number of oxygen ions is also 6, but they are not the same. Therefore, the correct answer is option 'A, B, C'.