WHAT IS CARBON ?

Carbon

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This article is about the chemical element. For other uses, see Carbon (disambiguation).

Carbon
6C
- ↑ C ↓ Si boron ← carbon → nitrogen
Carbon in the periodic table
Appearance
clear (diamond) & black (graphite) Spectral lines of Carbon
General properties
Name, symbol,number	carbon, C, 6
Pronunciation	/ˈkɑrbən/
Element category	polyatomic nonmetal
Group, period,block	14, 2, p
Standard atomic weight	12.011(1)
Electron configuration	[He] 2s2 2p2 2, 4
History
Discovery	Egyptians andSumerians[1] (3750 BC)
Recognized as an element by	Antoine Lavoisier[2] (1789)
Physical properties
Phase	solid
Density (near r.t.)	amorphous:[3] 1.8–2.1 g·cm−3
Density (near r.t.)	diamond: 3.515 g·cm−3
Density (near r.t.)	graphite: 2.267 g·cm−3
Sublimation point	3915 K, 3642 °C, 6588 °F
Triple point	4600 K, 10800[4][5] kPa
Heat of fusion	117 (graphite) kJ·mol−1
Molar heat capacity	6.155 (diamond) 8.517 (graphite) J·mol−1·K−1
Atomic properties
Oxidation states	4, 3[6], 2, 1[7], 0, −1, −2, −3,−4[8]
Electronegativity	2.55 (Pauling scale)
Ionization energies (more)	1st: 1086.5 kJ·mol−1
	2nd: 2352.6 kJ·mol−1
	3rd: 4620.5 kJ·mol−1
Covalent radius	77(sp³), 73(sp²), 69(sp) pm
Van der Waals radius	170 pm
Miscellanea
Crystal structure	diamond (diamond, clear)
	simple hexagonal (graphite, black)
Magnetic ordering	diamagnetic[9]
Thermal conductivity	900-2300 (diamond) 119-165 (graphite) W·m−1·K−1
Thermal expansion	(25 °C) 0.8 (diamond)[10]µm·m−1·K−1
Speed of sound(thin rod)	(20 °C) 18350 (diamond) m·s−1
Young's modulus	1050 (diamond)[10] GPa
Shear modulus	478 (diamond)[10] GPa
Bulk modulus	442 (diamond)[10] GPa
Poisson ratio	0.1 (diamond)[10]
Mohs hardness	10 (diamond) 1-2 (graphite)
CAS registry number	7440-44-0
Most stable isotopes
Main article: Isotopes of carbon
iso NA half-life DM DE (MeV) DP 11C syn 20 min β+ 0.96 11B 12C 98.9% 12C is stable with 6 neutrons 13C 1.1% 13C is stable with 7 neutrons 14C trace 5730 y β− 0.15 0 14N
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Carbon (from Latin: carbo "coal") is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. There are three naturally occurring isotopes, with¹²C and ¹³C being stable, while ¹⁴C is radioactive, decaying with a half-life of about 5,730 years.^[11] Carbon is one of the few elements known since antiquity.^[12]

There are several allotropes of carbon of which the best known are graphite, diamond, and amorphous carbon.^[13] The physical properties of carbon vary widely with the allotropic form. For example, diamond is highly transparent, while graphite is opaque and black. Diamond is the hardest naturally-occurring material known, while graphite is soft enough to form a streak on paper (hence its name, from the Greek word "γράφω" which means "to write"). Diamond has a very low electrical conductivity, while graphite is a very good conductor. Under normal conditions, diamond,carbon nanotube and graphene have the highest thermal conductivities of all known materials.

All carbon allotropes are solids under normal conditions with graphite being the most thermodynamically stable form. They are chemically resistant and require high temperature to react even with oxygen. The most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and other transition metal carbonyl complexes. The largest sources of inorganic carbon are limestones, dolomites andcarbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil and methane clathrates. Carbon forms more compounds than any other element, with almost ten million pure organic compounds described to date, which in turn are a tiny fraction of such compounds that are theoretically possible under standard conditions.^[14]

Carbon is the 15th most abundant element in the Earth's crust, and the fourth most abundant element in the universe by mass after hydrogen,helium, and oxygen. It is present in all known life forms, and in the human body carbon is the second most abundant element by mass (about 18.5%) after oxygen.^[15] This abundance, together with the unique diversity of organic compounds and their unusual polymer-forming ability at the temperatures commonly encountered on Earth, make this element the chemical basis of all known life.