Carbon

Allotropes An allotrope is a different form of the same element Carbon can bond with itself in different ways giving us 3 different materials Diamond Graphite Buckyballs and nanotubes. All are allotropes of Carbon.

Diamond Each carbon is bonded with strong covalent bonds 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 Each carbon atom is bonded to 3 other carbons with strong covalent bonds. Carbon atoms form sheets of six sided rings with the 4th valence electron delocalised between them.

Graphite Structure Carbon has 4 valence electrons to bond with. 3 are used for covalent bonds making rings.1 is delocalized. van der waals forces hold the sheets together.

relative orientation of the layers Graphite 1 relative orientation of the layers

Graphite 2 types of bond

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 electrons, 3653C) Insoluble (same reason)

Fullerenes Buckyballs: spherical Nanotubes: tube shaped Both have very interesting properties Super strong Conduct electricity and heat with very low resistance, a SUPERCONDUCTOR

Buckyballs Carbon atoms bond in units of e.g.,60 atoms (C60) forming a structure similar to a football with interlocking six sided and five sided rings (note, other types also exist). Presence of delocalised electrons leads to High electrical conductivity Stronger bonds so super strong materials