The allotropes of carbon have a variety of uses. Graphite, which conducts electricity, is used in electrodes. Because its atoms are arranged in layers, and because very weak bonds exist between the different layers, it is possible for these layers to slide over each other. This property makes graphite of use in pencils - layers are left on the page and produce the pencil marks - and in lubricants. Diamond, a very hard and attractive substance, is used as a gemstone and in drilling and cutting tools. Carbon black is used in inks and pigments, and as a strengthening agent in rubber. Carbon is also a constituent of plastics.
Silicon, a semiconductor, is widely used in the electronics industry in such items as transistors and printed circuits. It is also of great importance as a constituent of glass, concrete and clay.
Germanium too is a semiconductor, and was in fact used in the first transistor. Being transparent to infra-red light, it is also used in infra-red lenses.
Tin is used to plate steel, providing a surface that is very resistant to corrosion. Tin-plated products include food and drinks cans. Alloyed with lead, the metal is used in solder, and further alloys of which tin is a constituent include gun-metal (with copper, zinc and lead), and type metal (with antimony and lead). In addition to these uses, lead is also used in batteries and shotgun pellets.
