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?

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.

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Classify each of the following solids as ionic, metallic, molecular, network (covalent) or amorphous:

(i) Tetra phosphorous decoxide (P₄O₁₀)

(ii) Ammonium phosphate (NH₄)₃PO₄

(iii) SiC

(iv) I₂

(v) P₄

(vi) Plastic

(vii) Graphite

(viii) Brass

(ix) Rb

(x) LiBr

(xi) Si

What is the co-ordination number of atoms:
(i) in a cubic close packed structure?
(ii) in a body centred cubic structure?

Define the term ‘amorphous’. Give a few examples of amorphous solids.

What makes a glass different from a solid such as quartz? Under what conditions could quartz be converted into glass?

The Solid State

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?

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?