CARBÓN

Introducción

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

Clasificación

chalcogen
halógeno
Gas noble
Lantanoides
Actinoides
Elemento de tierras raras
Platino Metal Group
transuranium
No hay isótopos estables
Sólido
Líquido
Gas
Sólido (Predicho)

Descripción • Usos / Función

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

Propiedades físicas

Form:6 diamond
Punto de fusion:6
Punto de ebullición:6
Punto de sublimación:6 
Triple punto:6 
Punto crítico:6 
Form:6 graphite
Punto de fusion:6
Punto de ebullición:6
Punto de sublimación:6 3825 °C = 4098.15 K = 6917 °F
Triple punto:6 4489 °C = 4762.15 K = 8112.2 °F at 10.3 MPa
Punto crítico:6 
Densidad:7  3.513 (diamond)/2.2 (graphite) g/cm3

* - at 1 atm

Configuración electronica

Configuración electronica: [He] 2s2 2p2
Bloquear: p
Ocupado más alto nivel de energía: 2
Electrones de valencia: 4

Números cuánticos:

n = 2
ℓ = 1
m = 0
ms = +½

Vinculación

electronegatividad (escala de Pauling):8 2.55
Electropositivity (escala de Pauling): 1.45
Afinidad electronica:9 1.262119 eV
estados de oxidación: ±4
Función del trabajo:10 5.0 eV = 8.01E-19 J

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

termoquímica

Calor especifico: 0.709 J/g°C 12 = 8.516 J/mol°C = 0.169 cal/g°C = 2.035 cal/mol°C
Conductividad térmica: 129 (W/m)/K, 27°C 13
Calor de fusión: 
Calor de vaporización: 355.8 kJ/mol 14 = 29623.6 J/g
Estado de la materia Entalpía de formación (ΔHf°)15 entropía (S°)15 Energía libre de Gibbs (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

nucleido Masa 16 Media vida 16 spin nuclear 16 Energía de unión
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 ESTABLE 0+ 92.16 MeV
13C 13.0033548378(10) ESTABLE 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
Los valores marcados con # no son puramente derivan de los datos experimentales, pero al menos en parte, de las tendencias sistemáticas. Hace girar con débiles argumentos de asignación se incluyen entre paréntesis. 16

reacciones

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

Abundancia

Tierra - Los compuestos de origen: uncombined 42
Tierra - Agua de mar: 28 mg/L 43
Tierra -  Corteza:  200 mg/kg = 0.02% 43
Tierra -  litosfera:  0.018% 44
Tierra -  Atmósfera:  0.01% 44
Tierra -  Total:  446 ppm 45
Planeta mercurio) -  Total:  5.1 ppm 45
Venus -  Total:  468 ppm 45
Universo -  Total:  0.46% 46
condritas - Total: 2000 (relative to 106 atoms of Si) 47
Cuerpo humano - Total: 23% 48

Compuestos

Información de seguridad


Ficha de datos de seguridad de materiales - ACI Alloys, Inc.

Para más información

Enlaces 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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