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. Carbon's abundance, its unique diversity of organic compounds, and its unusual ability to form polymers at the temperatures commonly encountered on Earth, enables this element to serve as a common element of all known life. It is the second most abundant element in the human body by mass (about 18.5%) after oxygen.

Occurrence

Carbon is the fourth most abundant chemical element in the observable universe by mass after hydrogen, helium, and oxygen.Carbon is abundant in the Sun, stars, comets, and in the atmospheres of most planets.Some meteorites contain microscopic diamonds that were formed when the Solar System was still a protoplanetary disk.Microscopic diamonds may also be formed by the intense pressure and high temperature at the sites of meteorite impacts.

Uses

Amorphous carbon is formed when a material containing carbon is burned without enough oxygen for it to burn completely. This black soot, also known as lampblack, gas black, channel black or carbon black, is used to make inks, paints and rubber products. It can also be pressed into shapes and is used to form the cores of most dry cell batteries, among other things.

Reactions

Carbon forms carbon monoxide (CO) when heated in a limited supply of air and forms carbon dioxide when heated in a sufficient supply of air. The equilibrium between CO and CO2 is also known. 

Carbon is unreactive to hydrogen under ordinary conditions at any appreciable rate. However, hydrogen can react with powdered carbon in the presence of a finely divided nickel catalyst to form methane. 

The reaction of carbon with hydrogen and oxygen proceeds rapidly below 1000℃, but its reaction with nitrogen does not occur appreciably under comparable conditions. Carbon and nitrogen form the highly toxic cyanogen gas at temperatures above 2200℃. 

Reaction with halogens At high temperatures, graphite reacts readily with fluorine, F2, but not with other halogens. With an atmosphere of F2 at temperatures between 400℃ and 500℃ it gives CFx, where x 5 0.68
0.99. This species is black when x is low, silvery at x 5 0.9, and colorless when x is about 1. Above 600 C, the reaction proceeds explosively to form a mixture of carbon tetrafluoride, CF4, together with some C2F6 and C5F12.