Network Solids

Network Solid These are large macromolecules, giant structures of covalently bonded atoms in one, two or three dimensional arrays

Allotropes These are elements that exist in different physical forms with different physical properties but the same chemcial properties Allotropes of Sulphur

Allotropes of Carbon Diamonds and graphite are allotropes of carbon. Both form carbon dioxide and water when undergoing combustion but only graphite conducts electricity and diamond is one of the hardest substances known.

3-D Network Solids These network solids consist of covalently bonded atoms which form regular 3-D arrays or crystals.

The intermolecular bonds are the same as the intramolecular bonds – very strong bonds These solids will have very high mp & bp, will be extremely hard, not soluble and not conduct electricity

Examples of 3-D Network Solids Quartz – 3-D solid of Si & Oxygen Diamond

2-D Network Solids 2-D arrays or sheets The atoms within the sheets are held together with covalent bonds Weak Van der Waal forces hold the layers together Ex Mica

2-D Network Solids These solids will also have high mp & bp however they will be soft & the layers will slide over each other allowing them to be used as a lubricant Ex Graphite

Graphite Graphite is a 2-D array of C atos in layers of hexagons The electrons making up the ‘double bonds’ are actually delocalized throughout the structure The layers of hexagons are held in place by Van der Waal forces Graphite

1-D Network Solids These solids form networks in a 1-D array or fibre Consist of long chains held together by covalent bonds Forces between the adjacent chains are very weak so the solids form threads Solid & not water soluble Ex. Abestos – can be used as a fire retardant but is now known to cause cancer