It’s true that diamond, graphite and soot are all made of carbon and are in fact are pure forms of carbon. Let’s see how this is possible.

This property of substance in which the same substance is found in two different forms, is called Allotropy. This is just like the way as it is with ice and water. Ice and water both are same thing except in different forms or phases due to temp. But here, in the case of Allotropy, the difference is not of temperature but chemical (molecular) composition. Let us see what this actually means.

Graphite has a layered structure. Each carbon atom joins the other three carbon atoms to form the hexagonal ring structure. Such ring structures together form a flaky structure. The fourth electron of each carbon remains in free state due to weakness of the attraction force between the two layers, one layer may slip easily on the second layer, so the graphite is soft.

The carbon atoms in diamond, on the other hand, have strong bonds in three dimensions. In diamond, the atoms are very closely packed and each atom is connected to four other carbon atoms, giving it a very strong and rigid structure in three dimensions.

The carbon black or the soot of carbon is the crystalline composition. This is a powder.