Carbon

Allotropes Carbon can bond with itself in at least three different ways giving us 4 different materials –Diamond –Graphite –Buckyballs and nanotubes –Graphene

Diamond Carbons are bonded via sp 3 hybridization to 4 other carbon atoms forming a giant network covalent compound.

Properties of Diamond High melting point due to strong directional covalent bonds (3550  C) Extremely hard because it is difficult to break atoms apart or move them in relation to one another No electrical conductivity because electrons are localized in specific bonds Insoluble in polar and non-polar solvents because molecular bonds are stronger than any intermolecular forces

Graphite Carbon atoms are bonded via sp2 hybridization. Carbon atoms form sheets of six sided rings with p-orbitals perpendicular from plane of ring.

Graphite Structure Carbon has 4 valence e- to bond with. 3 are used for closest atoms in rings. 1 is delocalized in p- orbitals The presence of p- orbitals allows for strong van der waals forces that hold the sheets together

Properties of Graphite Different from Diamond –Conducts electricity because of delocalized electrons –Slippery can be used as lubricant, sheets can easily slip past each other (think of a deck of cards) Same as Diamond –High melting point (higher actually because of delocalized e-, 3653  C) –Insoluble (same reason)

Fullerenes Buckyballs: spherical Nanotubes: tube shaped Both have very interesting properties –Super strong –Conduct electricity and heat with low resistance –Free radical scavenger –Nanotechnology

Buckyballs Carbon atoms bond in units of 60 atoms (C-60) forming a structure similar to a soccerball with interlocking six sided and five sided rings. sp 2 hybridization Extra p-orbitals form pi bonds resulting in –Electrical conductivity –Stronger covalent bonds, therefore stronger materials

Graphene Nobel Prize in Physics in 2010 for discovery Single layer of hexagonal carbon atoms Graphite 1 layer thick Light, semiconductor, 200 times stronger than steel

Silicon and Silicon Dioxide (giant tetrahedral structures)