Sinonimi: C | atomic number 6
ETYM French carbone, from Latin carbo coal; cf. Skr. çrâ to cook.
An abundant nonmetallic tetravalent element occurring in three allotropic forms: amorphous carbon and graphite and diamond; occurs in all organic compounds; SYN. C, atomic number 6.
Nonmetallic element, symbol C, atomic number 6, relative atomic mass 12.011. It occurs on its own as diamond, graphite, and as fullerenes (the allotropes), as compounds in carbonaceous rocks such as chalk and limestone, as carbon dioxide in the atmosphere, as hydrocarbons in petroleum, coal, and natural gas, and as a constituent of all organic substances.
In its amorphous form, it is familiar as coal, charcoal, and soot. The atoms of carbon can link with one another in rings or chains, giving rise to innumerable complex compounds. Of the inorganic carbon compounds, the chief ones are carbon dioxide, a colorless gas formed when carbon is burned in an adequate supply of air; and carbon monoxide (CO), formed when carbon is oxidized in a limited supply of air. Carbon disulfide (CS2) is a dense liquid with a sweetish odor. Another group of compounds is the carbon halides, including carbon tetrachloride (tetrachloromethane, CCl4). When added to steel, carbon forms a wide range of alloys with useful properties. In pure form, it is used as a moderator in nuclear reactors; as colloidal graphite it is a good lubricant and, when deposited on a surface in a vacuum, obviates photoelectric and secondary emission of electrons. Carbon is used as a fuel in the form of coal or coke. The radioactive isotope carbon-14 (half-life 5,730 years) is used as a tracer in biological rese.
Arch. Analysis of interstellar dust has led to the discovery of discrete carbon molecules, each containing 60 carbon atoms. The C60 molecules have been named buckminsterfullerenes because of their structural similarity to the geodesic domes designed by US architect and engineer Buckminster Fuller.
The element has the following characteristic reactions. with air or oxygen It burns on heating to form carbon dioxide in excess air, or carbon monoxide in a limited supply of air.
C + O2 ® CO2 DH = -394 kJ mol-1.
2C + O2 ® 2CO.
With metal oxides.
It reduces many metal oxides at high temperatures. Fe2O3 + 3C ® 2Fe + 3CO with steam It forms water gas (a cheap, useful, industrial fuel) when steam is passed over white-hot coke.
C + H2O ® CO + H2.
With concentrated acids.
With hot, concentrated sulfuric or nitric acids it forms carbon dioxide.
Ugljenik, ugljik, nemetalan element, atomska težina 12, redni broj 6, znak C, javlja se nejedinjen u tri alotropna oblika (dva kristalna - dijamant i grafit - i jedan amorfan - drveni ugalj), u jedinjenju CO2 (gasu ugljenoj kiselini) i gotovo u svima organskim jedinjenjima.
Sinonimi: carbon copy
A copy made with carbon paper; SYN. carbon copy.
Papir za umnožavanje otisaka na pisaćoj mašini i ručno.