Question
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-centred cubic structure?
Solution
Co-ordination number : The total number of nearest neighbour atoms of a particular atom in a crystal lattice is known as its co-ordination number.
Example: In hexagonal close-packing (hcp) arrangement, each particle is surrounded by 12 equidistant spheres, i.e., 6 spheres in contact with in the same plane and 3 each in adjacent layers-one immediately above and the other immediately below. This, co-ordination number in hcp packing is 12.
Example: In hexagonal close-packing (hcp) arrangement, each particle is surrounded by 12 equidistant spheres, i.e., 6 spheres in contact with in the same plane and 3 each in adjacent layers-one immediately above and the other immediately below. This, co-ordination number in hcp packing is 12.
(ii) The coordination number of atoms
(a) In a cubic close-packed structure is 12
(b) In a body-centered cubic structure is 8
