CARBON

CARBON GROUP

Atomic number:	6
Group numbers:	14
Period:	2
Electronic configuration:	[He] 2s² 2p²
Formal oxidation number:	-4 +2 +4
Electronegativities:	2.55
Atomic radius / pm:	77.2
Relative atomic mass:	[12.0096, 12.0116]

Carbon has been known since ancient times. The origin of the name comes from the Latin word carbo meaning charcoal. Carbon has three forms: graphite, diamond and c60. Graphite form of carbon is a black, odourless, slippery solid and sublimes at 3825 °C. Diamond form is a clear or coloured; an extremely hard solid. C60 is Buckminsterfullerine. Carbon black burns readily with oxidants. Carbon is made by burning organic compounds with insufficient oxygen. There are close to ten million known carbon compounds, many thousands of which are vital to organic and life processes. Radiocarbon dating uses the carbon-14 isotope to date old objects. Black amorphous carbon (99.9 %) costs 48.40 € for 1000 g. Graphite powder (99.9 %) costs 46.50 € for 1000 g. Diamond powder (99.9 %) costs 265.70 € for 5 g. Fullerene powder (99.5 %) costs 762.20 € for 5 g.

PHYSICAL PROPERTIES
Density / g dm^-3:	3513	(diamant, 293 K)
	2260	(graphit, 293 K)
Molar volume / cm³mol^-1:	3.42	(diamant, 293 K)
	5.31	(graphit, 293 K)
Electrical resistivity / µΩcm:	1375	(20 °C)

THERMAL PROPERTIES
Thermal conductivity / W m^-1K^-1:	5.7
Melting point / °C:	3550
Boiling point / °C:	4827
Heat of fusion / kJ mol^-1:	105
Heat of vaporization / kJ mol^-1:	710.9
Heat of atomization / kJ mol^-1:	711.2

IONIZATION ENERGIES
First ionization energy / kJ mol^-1:	1086.46
Second ionization energy / kJ mol^-1:	2352.65
Third ionization energy / kJ mol^-1:	4620.50

ABUNDANCE OF ELEMENT
in the atmosphere / ppm:	336.7
in the Earth's crust / ppm:	200
in the oceans / ppm:	28

CRYSTALLOGRAPHIC DATA
Crystal structure:	hexagonal
Unit-cell dimensions / pm:	a=246.12, c=670.78
Space group:	P6₃/mmc

ISOTOPES
Isotope	Relative atomic mass	Mass percent (%)
¹²C	12	98.90(3)
¹³C	13.003354838(1)	1.10(3)
¹⁴C	14.003241988(4)	*

REDUCTION POTENTIALS
Balanced half-reaction	E^o / V
CO₂(g) + 2H⁺ + 2e^- → CO(g) + H₂O	- 0.12
2CO₂(g) + 2H⁺ + 2e^- → H₂C₂O₄	- 0.49
CO₂(g) + 2H⁺ + 2e^- → HCOOH	- 0.20
CNO^- + 2H₂O + 2e^- → CN^- + 2OH^-	- 0.97
2HCNO + 2H⁺ + 2e^- → (CN)₂(g) + 2H₂O	+0.33
(CN)₂(g) + 2H⁺ + 2e^- → 2HCN	+0.37
C₆H₄O₂ + 2H⁺ + 2e^- → C₆H₄(OH)₂	+0.699	(quinon/hydroquinone)
C₆H₄O₂ + 2H⁺ + 2e^- → C₆H₄(OH)₂	+0.696	(1 mol dm^-3 HCl)
C₆H₄O₂ + 2H⁺ + 2e^- → C₆H₄(OH)₂	+0.696	(1 mol dm^-3 HClO₄)
C₆H₄O₂ + 2H⁺ + 2e^- → C₆H₄(OH)₂	+0.696	(1 mol dm^-3 H₂SO₄)