Question

(i) What is meant by the term 'coordination number'? 

(ii) What is the coordination number of atoms:

(a) in a cubic close-packed structure? 

(b) in a body-centered cubic structure? 

Answer 1

(i) The number of nearest neighbours of any constituent particle present in the crystal lattice is called its coordination number. 

(ii) The coordination number of atoms

 (a) in a cubic close-packed structure is 12, and

 (b) in a body-centred cubic structure is 8