Carbon (C)

Atomic number is defined by proton count. That is why six protons identify carbon regardless of isotope or chemical compound. Neutral carbon has six electrons because positive and negative charge balance.

For ¹²C, the mass number 12 means 6 protons + 6 neutrons. ¹³C has 7 neutrons, while radioactive ¹⁴C has 8.

Its ground-state electron configuration is 1s² 2s² 2p². The electrons in the n = 2 shell are the four outer electrons: two in 2s and two in 2p.

Those four outer electrons are the starting point for understanding carbon’s ability to form four strong covalent bonds and the enormous diversity of carbon chemistry.

The 1s orbital contains the two core electrons. The second shell contains the four valence electrons: two in 2s and two in 2p.

In the ground-state orbital-box picture, the two 2p electrons occupy separate p orbitals before pairing, following Hund’s rule. Bonding descriptions such as sp³, sp² and sp are separate hybridization models.

Carbon is neither strongly driven to lose four electrons nor to gain four as simple ions under ordinary molecular conditions. Sharing electrons through covalent bonds is therefore central to its chemistry.

Different bonding patterns allow single, double and triple bonds, while carbon–carbon bonding lets atoms connect into chains, rings, sheets and networks. Hybridization models such as sp³, sp² and sp help organize the geometry of many of these structures.

Diamond forms a rigid three-dimensional covalent network in which each carbon is tetrahedrally connected. Graphite consists of strongly bonded hexagonal sheets with much weaker interactions between the sheets.

That structural difference changes hardness, electrical behavior, density and how the material responds to force. It is one of chemistry’s clearest demonstrations that structure controls properties.

You can think of graphite as many graphene-like layers stacked together. Isolating a single layer reveals unusual mechanical, electrical and thermal properties associated with a two-dimensional carbon lattice.

Graphene became a major research material after it was isolated and characterized in 2004; the work of Andre Geim and Konstantin Novoselov was recognized with the 2010 Nobel Prize in Physics.

¹²C has 6 neutrons and is the dominant natural isotope. ¹³C has 7 neutrons and is also stable. ¹⁴C has 8 neutrons and is radioactive.

Because isotopes share the same proton count, they are all carbon and have closely related chemistry. Their different masses and nuclear stability make them useful in areas such as isotope tracing and radiocarbon dating.

¹⁴C is continually created in the atmosphere and becomes part of atmospheric carbon dioxide. Through photosynthesis and food webs, living organisms exchange carbon with the environment.

After an organism dies, that exchange largely stops and the existing ¹⁴C decays toward ¹⁴N with a half-life of about 5,730 years. Measuring the remaining isotope, together with calibration, gives an estimate of age.

Biological molecules such as carbohydrates, lipids, proteins and nucleic acids rely on carbon frameworks. Carbon can form chains, branches and rings while bonding with hydrogen, oxygen, nitrogen, phosphorus, sulfur and other elements.

This versatility makes carbon an unusually effective structural basis for the chemistry of known life.

Fast biological processes include photosynthesis, respiration and decomposition. Ocean exchange also moves carbon between air and water.

Slow geological processes include weathering, carbonate formation, burial, tectonics and volcanic return. Carbon can therefore remain in one reservoir for days, centuries or millions of years depending on the pathway.

RSC gives a reference sublimation temperature around 4098 K. Carbon’s full phase behavior is strongly pressure-dependent, and different allotropes complicate the story.

That is why Element Lookup does not present a single ordinary “carbon melting point” as though carbon behaved like a simple metal at one atmosphere.

Carbon is present in Earth’s atmosphere and oceans, throughout organisms and soils, and in vast quantities stored in rocks such as carbonates. It also occurs in fossil fuels and in elemental forms including graphite and diamond.

Because the reservoirs are so different, a single “carbon location map” would be misleading. The page therefore separates natural graphite production from the broader carbon-cycle view.