Carbon atoms can connect to each other by forming several kinds of chemical bonds.  The different bonding schemes among the carbon atoms can form different crystalline structures.  Three of these are described below.  Graphite: Space Group                     C6/mmc  C-centered hexagonal Lattice parameters              a = 2.4612 Angstroms  c = 6.7079 Angstroms Atoms/unit cell                 4 Cell volume                     35.189 x 10-24 cm3 X-ray density                   2.2670 g/cm3 Crystalline graphite consists of sheets of carbon atoms arranged in a honeycomb like structure with three nearest neighbors, with a C-C bond distance of 1.415 Angstroms, within the sheet.  The layers are held by weak forces, and separated by 3.35 Angstroms.  Diamond: Space Group                     Fd3m    face-centered cubic Lattice parameters              a = 3.5670 Angstroms Atoms/unit cell                 8 Cell volume                     45.385 x 10-24 cm3 X-ray density                   3.5155 g/cm3 The carbon atoms within diamond are arranged into a rigid, three-dimensional network, with each atom tetrahedrally bonded to its nearest neighbors and separated by 1.544 Angstroms.  Buckminster Fullerene: Space Group                     Fm3m  body-centered cubic Lattice parameters              a = 14.14 Angstroms Atoms/unit cell                 240  (4 molecules) Cell volume                     2.827 x 10-21 cm3 X-ray density                   1.693 g/cm3 The carbon atoms in the Buckminster fullerenes are arranged into discrete molecular units that are somewhat like soccer balls. These spheres are held together by weak intermolecular forces to form a cubic structure.  Click here to find out how to calculate the density of a crystal using these data.