w hot i the we? ALTON BANKS Souihwest Texas State University

San Marcos. TX 78666

Symbol: C Atomic number: 6 Atomic weight: 12.01 Melting point: 3823.2 K Bailing point: No date Density: 2.26 g/cm3 graphite

3.51 g/cm3 diamond

Carbon might well he described as the chameleon of the elements. The three major forms of this element run the gamut from one of the softest to one of the hardest materials known. Known since prehistoric times, carbon is unique amone the elements since i t forms more comnounds than all otherlements combined. Carbon-in bot~elemental and com~ound forms-is nerhans more widelv distributed than any bther element. A; important part o i t h e carbonfnitro- genloxygen cycles that provide energy for stars, carbon also accounts for ahout 0.03% of the atmosphere in the form of COz. In the earth's crust chalk, limestone, marble, and other carbonates compose an important portion of carbon's inor- ganic compounds.

for brushes in electrical motors, electrodes in fuel cells and electric furnaces, furnace linings, extrusion dies, shields and moderators in nurlear reactors, and the uhiauitous "lead" in pencils. The amorphous form of carbon called charcoal is widely used as a decolorizing agent and an absorbent for gases. The highly prized form of crystalline carbon, dia- mond, is to many minds without equal in the world of gems. While the elemental forms of carbon are a great cog in the wheel of today's industry, petroleum compounds form the oils, greases, and fuels that power our manifold motorized vehicles. No survey of carbon and its compounds, however brief, would be complete without a mention of the thousands of substances produced by the chemical industry and con- verted into the many polymeric materials that have changed, in large part, our society.

Finally, we should not overlook the pivotal importance of carbon compounds in the organic microcosm which is the human being.

Some of these applications are shown on "The Periodic Tables Videodisc" in frames 36363-36380.

Sources "KC? Discoverer: Exploring the Propecties of the Chemical Elements?": JCE: Saliuarr

11911. iRI1!. ~. ~

The amorphous forms--coal and lignite-provide energy lhnh' \ .I The 18?r#d.r i'ahl V ~lnnW .I< E S i r . ,r. 19r9.<$>1 0 1 l t , ~ c I

as well as raw materials for the many applirations of "manu- I1.ll.r a i f n r " . . , r , A P h > ~ . . : l rn, . , \%el., h. lhr , , i b,., .Th.r'h.n,, r l R 2 0 k r < C.c~cland.Oli. 19.1 I,.. p ll ,

factured"carbon and e ra~h i te in todav's world. Widelv used

Volume 67 Number 2 February 1990 109