CARBONO

Introdução

Número atômico: 6
Grupo: 14 or IV A
Peso atômico: 12.0107
Período: 2
Número CAS: 7440-44-0

Classificação

Calcogênio
halogênio
Gás nobre
Lantanóides
Actinóide
Terra-rara
Platinum Metal Group
Transuranium
Não Isótopos Estáveis
Sólido
Líquido
Gás
Sólido (previsto)

Descrição • Usos / Função

Carbon, an element of prehistoric discovery, is very widely distributed in nature. It is found in abundance in the sun, stars, comets, and atmospheres of most planets. Carbon in the form of microscopic diamonds is found in some meteorites. Natural diamonds are found in kimberlite of ancient volcanic “pipes,” such as found in South Africa, Arkansas, and elsewhere. Diamonds are now also being recovered from the ocean floor off the Cape of Good Hope. About 30% of all industrial diamonds used in the U.S. are now made synthetically. The energy of the sun and stars can be attributed at least in part to the well-known carbon-nitrogen cycle. Carbon is found free in nature in three allotropic forms: amorphous, graphite, and diamond. A fourth form, known as “white” carbon, is now thought to exist. Graphite is one of the softest known materials while diamond is one of the hardest. Graphite exists in two forms: alpha and beta. These have identical physical properties, except for their crystal structure. Naturally occurring graphites are reported to contain as much as 30% of the rhombohedral (beta) form, whereas synthetic materials contain only the alpha form. The hexagonal alpha type can be converted to the beta by mechanical treatment, and the beta form reverts to the alpha on heating it above 1000°C. In 1969 a new allotropic form of carbon was produced during the sublimation of pyrolytic graphite at low pressures. Under free-vaporization conditions above ~2550 K, “white” carbon forms as small transparent crystals on the edges of the basal planes of graphite. The interplanar spacings of “white” carbon are identical to those of carbon form noted in the graphitic gneiss from the Ries (meteoritic) Crater of Germany. “White” carbon is a transparent birefringent material. Little information is presently available about this allotrope. Of recent interest is the discovery of all-carbon molecules, known as “buckyballs” or fullerenes, which have a number of unusual properties. These interesting molecules, consisting of 60 or 70 carbon atoms linked together, seem capable of withstanding great pressure and trapping foreign atoms inside their network of carbon. They are said to be capable of magnetism and superconductivity and have potential as a nonlinear optical material. Buckyball films are reported to remain superconductive at temperatures as high as 45 K. In combination, carbon is found as carbon dioxide in the atmosphere of the earth and dissolved in all natural waters. It is a component of great rock masses in the form of carbonates of calcium (limestone), magnesium, and iron. Coal, petroleum, and natural gas are chiefly hydrocarbons. Carbon is unique among the elements in the vast number and variety of compounds it can form. With hydrogen, oxygen, nitrogen, and other elements, it forms a very large number of compounds, carbon atom often being linked to carbon atom. There are close to ten million known carbon compounds, many thousands of which are vital to organic and life processes. Without carbon, the basis for life would be impossible. While it has been thought that silicon might take the place of carbon in forming a host of similar compounds, it is now not possible to form stable compounds with very long chains of silicon atoms. The atmosphere of Mars contains 96.2% CO2. Some of the most important compounds of carbon are carbon dioxide (CO2), carbon monoxide (CO), carbon disulfide (CS2), chloroform (CHCl3), carbon tetrachloride (CCl4), methane (CH4), ethylene (C2H4), acetylene (C2H2), benzene (C6H6), ethyl alcohol (C2H5OH), acetic acid (CH3COOH), and their derivatives. Carbon has thirteen isotopes. Natural carbon consists of 98.89% 12C and 1.11% 13C. In 1961 the International Union of Pure and Applied Chemistry adopted the isotope carbon-12 as the basis for atomic weights. Carbon-14, an isotope with a half-life of 5715 years, has been widely used to date such materials as wood, archeological specimens, etc. 1

• "...a small amount of carbon in iron greatly improves its hardness." 2
• "37th most produced chemical in the United States in 1995 - 1.50 megatonnes." 3
• "Taste and odor control [in chemical water analysis]" 4
• "A pebble bed nuclear reactor is schematically depicted as a funnel-shaped container through which tennis-ball size "pebbles" of fuel are circulated. Each pebble is made of graphite and carbon and contains about 15,000 kernels of fuel. Each kernel has a core of uranium that is coated with a layer each of porous carbon, pyrolytic carbon (which is similar to graphite), silicon carbide, and then a second layer of pyrolytic carbon. These layers are used to moderate the speed of neutrons, helping to control the nuclear reactions of the fuel, and to provide a fireproof seal." 5

Propriedades físicas

Form:6 diamond
Ponto de fusão:6
Ponto de ebulição:6
Ponto de sublimação:6 
Ponto Triplo:6 
Ponto crítico:6 
Form:6 graphite
Ponto de fusão:6
Ponto de ebulição:6
Ponto de sublimação:6 3825 °C = 4098.15 K = 6917 °F
Ponto Triplo:6 4489 °C = 4762.15 K = 8112.2 °F at 10.3 MPa
Ponto crítico:6 
Densidade:7  3.513 (diamond)/2.2 (graphite) g/cm3

* - at 1 atm

Configuração Electron

Configuração Electron: [He] 2s2 2p2
Quadra: p
Mais alto nível de energia Ocupado: 2
Elétrons de valência: 4

Números quânticos:

n = 2
ℓ = 1
m = 0
ms = +½

Colagem

Eletronegatividade (escala Pauling):8 2.55
Electropositivity (escala Pauling): 1.45
Electron Affinity:9 1.262119 eV
oxidação Unidos: ±4
Função no trabalho:10 5.0 eV = 8.01E-19 J

potencial de ionização   eV 11  kJ/mol  
1 11.2603    1086.5
2 24.38332    2352.6
potencial de ionização   eV 11  kJ/mol  
3 47.8878    4620.5
4 64.4939    6222.7
potencial de ionização   eV 11  kJ/mol  
5 392.087    37830.6
6 489.99334    47277.2

Termoquímica

Calor específico: 0.709 J/g°C 12 = 8.516 J/mol°C = 0.169 cal/g°C = 2.035 cal/mol°C
Condutividade térmica: 129 (W/m)/K, 27°C 13
Calor de fusão: 
Calor da vaporização: 355.8 kJ/mol 14 = 29623.6 J/g
Estado da matéria Entalpia de formação (ΔHf°)15 entropia (S°)15 Gibbs Energia Livre (ΔGf°)15
(kcal/mol) (kJ/mol) (cal/K) (J/K) (kcal/mol) (kJ/mol)
(s) 0 0 1.361 5.694424 0 0
(s) 0.4533 1.8966072 0.568 2.376512 0.6930 2.899512
(g) 171.291 716.681544 37.7597 157.9865848 160.442 671.289328

isótopos

nuclide Massa 16 Meia vida 16 spin nuclear 16 Energia de ligação
10C 10.0168532(4) 19.290(12) s 0+ 61.12 MeV
11C 11.0114336(10) 20.334(24) min 3/2- 73.84 MeV
12C 12 ESTÁVEL 0+ 92.16 MeV
13C 13.0033548378(10) ESTÁVEL 1/2- 97.44 MeV
14C 14.003241989(4) 5.70(3) x 103 years 0+ 105.51 MeV
15C 15.0105993(9) 2.449(5) s 1/2+ 107.06 MeV
16C 16.014701(4) 0.747(8) s 0+ 111.41 MeV
17C 17.022586(19) 193(5) ms (3/2+) 112.03 MeV
18C 18.02676(3) 92(2) ms 0+ 116.37 MeV
19C 19.03481(11) 46.2(23) ms (1/2+) 116.99 MeV
20C 20.04032(26) 16(3) ms [14(+6-5) ms] 0+ 119.47 MeV
21C 21.04934(54)# <30 ns (1/2+)# 119.16 MeV
22C 22.05720(97)# 6.2(13) ms [6.1(+14-12) ms] 0+ 119.78 MeV
8C 8.037675(25) 2.0(4) x 10-21 s [230(50) keV] 0+ 24.85 MeV
9C 9.0310367(23) 126.5(9) ms (3/2-) 39.07 MeV
Os valores marcados # não são puramente derivado a partir de dados experimentais, mas, pelo menos, parcialmente a partir de tendências sistemáticas. Gira com argumentos de atribuição fracos estão entre parênteses. 16

reações

2 Al2O3 + 3 C → 4 Al + 3 CO2  17
Al2O3 + 3 C + 3 Cl2 → 2 AlCl3 + 3 CO  18
Bi2O3 (s) + 3 C (s graphite) → 3 Bi (s) + 3 CO (g) 19
2 C (s graphite) + 1 O2 (g) → 2 CO (g) 20
2 C (s graphite) + 2 H2 (g) + 1 O2 (g) → CH3COOH (ℓ acetic acid) 21
C12H22O11 (s sucrose) → 12 C (s graphite) + 11 H2O (g) 22
2 Ca3(PO4)2 (s beta) + 6 SiO2 (s quartz) + 10 C (s graphite) → P4 (g) + 6 CaSiO3 (ℓ) + 10 CO (g) 23
CaO (s) + 3 C (s) → CaC2 (s) + CO (g) 24
CF2Cl2 (g) + 2 Na2C2O4 (s) → 2 NaF (s) + 2 NaCl (s) + 4 CO2 (g) + 1 C (s) 25
CH4 (g methane) → C (g) + 4 H (g) 26
CO2 (g) + 1 C (s) → 2 CO (g) 27
2 CuO (s) + 1 C (s graphite) → 2 Cu (s) + CO2 (g) 28
2 Fe2O3 (s hematite) + 3 C (s graphite) → 4 Fe (s alpha) + 3 CO2 (g) 29
Fe2O3 (s hematite) + 3 C (s graphite) → 2 Fe (s alpha) + 3 CO (g) 30
FeO (s) + 1 C (s graphite) → Fe (s alpha) + CO (g) 31
H2 (g) + 2 C (s graphite) + 1 N2 (g) → 2 HCN (g) 32
Na2SO4 (s) + 4 C (s graphite) → Na2S (s) + 4 CO (g) 33
SiO2 (s quartz) + 2 C (s graphite) → Si (ℓ) + 2 CO (g) 34
SiO2 (g) + 2 C (s graphite) + 2 Cl2 (g) → SiCl4 (g) + 2 CO (g) 35
2 TiO2 (s rutile) + 3 C (s graphite) + 4 Cl2 (g) → 2 TiCl4 (g) + CO2 (g) + 2 CO (g) 36
TiO2 (s rutile) + 1 C (s graphite) + 2 Cl2 (g) → TiCl4 (g) + CO2 (g) 37
W (s) + 1 C (s graphite) → WC (s) 38
ZnO + 1 C → Zn + CO  39
2 Ca3(PO4)2 (s beta) + 6 SiO2 (s quartz) + 10 C (s graphite) → P4 (g) + 6 CaSiO3 (s wollastonite) + 10 CO (g) 40
13 C (s graphite) + 3 Cr2O3 (s) → 2 Cr3C2 (s) + 9 CO (g) 41

Abundância

Terra - Os compostos de origem: uncombined 42
Terra - A água do mar: 28 mg/L 43
Terra -  crosta:  200 mg/kg = 0.02% 43
Terra -  litosfera:  0.018% 44
Terra -  Atmosfera:  0.01% 44
Terra -  Total:  446 ppm 45
Planeta Mercúrio) -  Total:  5.1 ppm 45
Vênus -  Total:  468 ppm 45
Universo -  Total:  0.46% 46
condritos - Total: 2000 (relative to 106 atoms of Si) 47
Corpo humano - Total: 23% 48

compostos

Informação de Segurança


Material Safety Data Sheet - ACI Alloys, Inc.

Para maiores informações

Links externos:

revistas:
(1) Perkins, Sid. Tiny Diamonds May Set Earlier Date for First Life. Science News, August 2, 2008, pp 13.
(2) Musser, George. A Large Lump of Coal. Scientific American, January 2010, pp 26.
(3) Castelvecchi, Davide. Origins Roundup: Carbon. Scientific American, September 2009, pp 83.
(4) Ehrenberg, Rachel. The Element Tin Flout's Carbon's Chemistry Rules. Science News, October 24, 2009, pp 13.
(5) Jenkins, Keith A. Graphene in High-Frequency Electronics. American Scientist, September-October 2012, pp 388-397.

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