Answer to Question #159927 in General Chemistry for John

Question

Research and describe, using diagrams, the type of bonding and structure present in two allotropes of carbon.

Answer 1

Allotropes of carbon

In all allotropes, the carbon atoms are joined by strong covalent bonds; however, they have different structures.

Diamond

Diamond is probably the most well-known carbon allotrope. The carbon atoms are arranged in a lattice, a variation of the face-centered cubic crystal structure. It has superlative physical qualities, most of which originate from the strong covalent bonding between its atoms. Each carbon atom in a diamond is covalently bonded to four other carbons in a tetrahedron. Together, these tetrahedrons form a three-dimensional network of six-membered carbon rings in the chair conformation, allowing for zero bond-angle strain. This stable network of covalent bonds and hexagonal rings is why diamond is so solid as a substance.

Graphite

Graphite contains layers of carbon atoms.

Graphite has a layered, planar structure. In each layer, the carbon atoms are arranged in a hexagonal lattice with a separation of 0.142 nm, and the distance between planes (layers) is 0.335 nm. The two known forms of graphite, alpha (hexagonal) and beta (rhombohedral) have very similar physical properties (except that the layers stack slightly differently). The hexagonal graphite may be either flat or buckled.

Each carbon atom is bonded into its layer with three strong covalent bonds, leaving each atom with a spare electron, which forms a delocalized 'sea' of electrons loosely bonding the layers together by van der Waals forces of attraction. These delocalized electrons can all move along together – making graphite an excellent electrical conductor.