• Carbon contains six electrons with electronic structure: (1s2), (2s), (2px), (2py), (2pz). Outer s orbital together with three p orbitals form the chemical bonds of carbon with other atoms. • Conventionally, solid carbon has two main structures called allotropic forms: diamond and graphite: - Diamond is tetrahedrally bonded through sp3 hybrid bonds that form a 3D network. - Graphite has a layered structure with each layer called graphene formed by sp2 hybrid bonds that make 120° angles with each other. Hexagonal graphene sheets are held together by weak van der Waals forces.
C60 y x
Allotropies of C
Types of spn hybridization:
• Graphene is a flat monolayer of sp2-bonded carbon (C) atoms tightly packed into a 2D honeycomb lattice. It is a basic building block for graphitic materials of all other dimensionalities. • It can be wrapped up into 0D fullerene, rolled into 1D nanotube, or stacked into 3D graphite. • The C-C bond length in graphene is about 0.142 nm. • Andre Geim and Konstantin Novoselov shared the Nobel Prize in Physics 2010 for the groundbreaking experiments regarding the 2D graphene.
Type of spn hybridisation Digonal sp Trigonal sp2 Tetrahedral sp3
Example Acetylene C2H2 Ethylene C2H4 Methane CH4
Orbitals used for bond s, px s, px, py s, px, py, pz
Bond angle 180° 120° 109.5°
Digonal bond (sp) Trigonal bonds (sp2)
Tetrahedral bonds (sp3)
Fullerene (C60): • C60 was named after the architect R. Buckminster Fuller who designed the geodesic dome that resembles the structure of C60. • C60 has 12 pentagonal (5 sided) and 20 hexagonal (6 sided) faces symmetrically arrayed to form a molecular ball. • Existence of C60 had been envisioned by theoretical chemists for years before it was experimentally confirmed by Huffiman and Kratschmer. • In fact, C60 has the same geometric