Allotropes • Carbon can bond with itself in at least three different ways giving us 3 different materials • Diamond • Graphite • Buckyballs and nanotubes
Diamond • Carbons are bonded via sp3 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-, 3653C) • 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
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. • sp2 hybridization • Extra p-orbitals form pi bonds resulting in • Electrical conductivity • Stronger covalent bonds, therefore stronger materials