CARBON is nonmetallic and tetravalent.Carbon is one of the few elements known to man since antiquity.There are several allotropes of carbon of which  we known are graphite,diamond,and amorphous carbon.The physical properties of carbon are different according to its allotropic form.

1.  An element found in all organic compounds is - Carbon
2. Which is the purest form of carbon  -  Diamond
3. Black lead is  - Graphite
4. The only non metal which is a good conductor of electricity - Graphite
5. The element with highest melting point - Carbon (4000K) (Diamond)

• Diamond is highly transparent,while graphite is opaque and black.
• Diamond is  the hardest material in world,while graphite is very soft that we can make  a streak on paper.
• Diamond has a very low electrical conductivity,while graphite is a very good conductor of electricity. 
• Under normal conditions,diamond has the highest thermal conductivity  but graphite is the most thermo dynamically stable.

All forms of carbon are highly stable,requiring high temperature to react even with oxygen.The most common oxidation state of carbon in inorganic compounds is +4,while +2 is found in carbon monoxide .The largest sources of inorganic carbon are limestones,dolomites and carbon dioxide,but nominal quantities  in organic deposits of coal,peat,oil and methane .Carbon forms more compounds than any other element.

Carbon is the fourth most abundant element in the universe by mass after hydrogen,helium and oxygen.It is present in all known lifeforms,and in the human body,carbon is the second most abundant element by mass (about 18.5%) after oxygen.