Carbon,  ₆C

Graphite (left) and diamond (right), two allotropes of carbon
General properties
Allotropes	graphite, diamond
Appearance	graphite: black diamond: clear
Standard atomic weight (Ar, standard)	[12.0096, 12.0116]
Carbon in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson – ↑ C ↓ Si boron ← carbon → nitrogen
Atomic number (Z)	6
Group	group 14 (carbon group)
Period	period 2
Block	p-block
Element category	reactive nonmetal, sometimes considered a metalloid
Electron configuration	[He] 2s2 2p2
Electrons per shell	2, 4
Physical properties
Phase at STP	C: Solid
Sublimation point	3915 K ​(3642 °C, ​6588 °F)
Density (near r.t.)	amorphous: 1.8–2.1 g/cm3 graphite: 2.267 g/cm3 diamond: 3.515 g/cm3
Triple point	4600 K, ​10,800 kPa
Heat of fusion	graphite: 117 kJ/mol
Molar heat capacity	graphite: 8.517 J/(mol·K) diamond: 6.155 J/(mol·K)
Atomic properties
Oxidation states	−4, −3, −2, −1, 0, +1, +2, +3,+4 (a mildly acidic oxide)
Electronegativity	Pauling scale: 2.55
Ionization energies	1st: 1086.5 kJ/mol 2nd: 2352.6 kJ/mol 3rd: 4620.5 kJ/mol (more)
Covalent radius	sp3: 77 pm sp2: 73 pm sp: 69 pm
Van der Waals radius	170 pm
Spectral lines of carbon
Other properties
Natural occurrence	C: Primordial
Crystal structure	graphite: ​simple hexagonal (black)
Crystal structure	diamond: ​face-centered diamond-cubic (clear)
Speed of sound thin rod	diamond: 18,350 m/s (at 20 °C)
Thermal expansion	diamond: 0.8 µm/(m·K) (at 25 °C)
Thermal conductivity	graphite: 119–165 W/(m·K) diamond: 900–2300 W/(m·K)
Electrical resistivity	graphite: 7.837 µΩ·m
Magnetic ordering	diamagnetic
Magnetic susceptibility	−5.9·10−6 (graph.) cm3/mol
Young's modulus	diamond: 1050 GPa
Shear modulus	diamond: 478 GPa
Bulk modulus	diamond: 442 GPa
Poisson ratio	diamond: 0.1
Mohs hardness	graphite: 1–2 diamond: 10
CAS Number	7440-44-0
History
Discovery	Egyptians and Sumerians (3750 BCE)
Recognized as an element by	Antoine Lavoisier (1789)
Main isotopes of carbon
Iso­tope Abun­dance Half-life (1/2) Decay mode Pro­duct 11C syn 20 min β+ 11B 12C 98.9% stable 13C 1.1% stable 14C trace 5730 y β− 14N
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Carbon is a very important chemical element, with a chemical symbol of C. All known life on Earth needs it to survive. Carbon has atomic mass 12 and atomic number 6. It is a nonmetal, meaning that it is not a metal.

When iron is alloyed with carbon, hard steel is formed. Carbon in the form of coal is an important fuel.