"coal") is a chemical element with symbol C and atomic number 6.It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds.
For example, graphite is opaque and black while diamond is highly transparent.
Graphite is soft enough to form a streak on paper (hence its name, from the Greek verb "γράφειν" which means "to write"), while diamond is the hardest naturally occurring material known.
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.
Although thermodynamically prone to oxidation, carbon resists oxidation more effectively than elements such as iron and copper that are weaker reducing agents at room temperature.