Elemental carbon exists in two well-defined allotropic crystalline forms: diamond and graphite.
Other forms with little crystallinity are vegetal carbon and black fume.
Symbol: C; atomic no: 6; atomic wt: 12.011; valency: 2, 3, or 4; relative density: 1.8–2.1 (amorphous), 1.9–2.3 (graphite), 3.15–3.53 (diamond); sublimes at 3367±25°C; boiling pt: 4827°C 1. Symbol C A naturally abundant, nonmetallic element that occurs in all organic compounds and can be found in all living things. Proteins, sugars, fats, and even DNA all contain many carbon atoms.
a nonmetallic element found combined with other elements in all organic matter and in a pure state as diamond and graphite. Diamonds and graphite are pure forms, and carbon is a major part of coal, petroleum, and natural gas. The element carbon is also important, however, outside the chemistry of living things.
[See Periodic Table of the Elements] Carbon occurs naturally as carbon-12, which makes up almost 99 percent of the carbon in the universe; carbon-13, which makes up about 1 percent; and carbon-14, which makes up a minuscule amount of overall carbon but is very important in dating organic objects.
Just the facts Carbon: From stars to life As the sixth-most abundant element in the universe, carbon forms in the belly of stars in a reaction called the triple-alpha process, according to the Swinburne Center for Astrophysics and Supercomputing.
In older stars that have burned most of their hydrogen, leftover helium accumulates.
Each helium nucleus has two protons and two neutrons.
But in graphite, each carbon atom bonds only to three others in a much looser arrangement of layers, each of which is weakly bonded to neighboring layers.
Because individual layers of carbon in graphite are so loosely connected, they are easily scraped away, which is why it is used as pencil "lead" for writing.
Symbol C An abundant nonmetallic element that occurs in many inorganic and in all organic compounds, exists freely in amorphous, graphite, and diamond forms and as a constituent of coal, limestone, and petroleum, and is capable of chemical self-bonding to form an enormous number of chemically, biologically, and commercially important molecules.
Other significant allotropes include fullerenes and nanotubes.
This black soot, also known as lampblack, gas black, channel black or carbon black, is used to make inks, paints and rubber products.