Question

why graphite is poor than diamond?
why diamond is harder than graphite?
why graphite is smoother?

Answer 1

Why graphite is poor than diamond?
Graphite and diamond are both made from carbon, which has 4 electrons in its outer shell. Diamond has four bonds, meaning there are no free electrons. Graphite has three bonds giving it a free electron.

Why diamond is harder than graphite?
In diamond the four valence electrons of a carbon atom form covalent (σ - bonds) bonds with adjacent carbon atoms. The electrons of a single carbon atom are arranged in orbitals forming the four corners of a tetrahedron (due to sp3 hybridization). All the bonds are of the same length - 1.54 Angstroms, and with the same bond angle (109.47 degrees). The covalent bonds give diamond it’s harder.

Why graphite is smoother?
In graphite, the three valence electrons of a carbon atom form covalent bonds (σ - bonds) with adjacent carbon atoms. The electrons of a single carbon atom are arranged in orbitals forming the vertices of a triangle lying in a plane (due to sp2 hybridization). The fourth valence electron, however is weakly bound to all the three neighboring carbon atoms