Carbon allotropes, adsorption and the carbon cycle
One element forms a hard network, soft layers, molecular cages and porous adsorbents.
Learning goals: connect carbon bonding to allotrope properties; distinguish adsorption from absorption; explain activated-carbon action; follow carbon through photosynthesis, respiration, combustion, oceans and rocks; balance simple carbon redox equations.
1. Carbon and its structures
Carbon is a group 14 nonmetal with four valence electrons. It can form four strong covalent bonds and shows oxidation states from −4 in methane to +2 in carbon monoxide and +4 in carbon dioxide. Elemental carbon has oxidation state 0. Allotropes contain the same element but differ in bonding and arrangement, so their physical properties can be dramatically different.