Question

grafite and dimond both are made up of pure carbon (free state) but why the dimond is more stronger than grafite .......don't give week answer if you don't know please don't give answer

Answer 1

The molecular structure is different. Carbon atoms in graphite are bonded in layers with only weak covalent bonds holding the layers together. When you write with a pencil some of the layers detach from the pencil lead and attach to the paper. Carbon atoms in diamond are bonded in a stronger tetrahedron pattern.

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Answer 2

Diamond and graphite are both made up of carbon atoms, except they have different physical form and properties, due to the nature of bonds formed between the carbon atoms.In diamond the 4 valence electrons of a carbon atom form covalent (sigma 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 hybridisation). All the bonds are of the same length - 1.54 Angstroms, and with the same bond angle ( 109.47 degrees). It is the covalent bonds  that gives diamond its strength.In graphite, 3 valence electrons of a carbon atom form covalent bonds(sigma bonds) with adjacent carbon atoms. The electrons of a single carbon atom are arranged in orbitals forming the the vertices of a triangle lying in a plane (due to sp2 hybridisation). The fourth valence electron, however is weakly bound to all the three neighboring carbon atoms, and is free to move around, not only giving graphite its conductivity, but also stabilizing the layer. This electron causes the carbon-carbon distance in the layer to be 1.42 Angstroms in comparison to 1.54 Angstroms in diamond. These layers are held together, however by weak Van der Waals forces (the London dispersion  component). These layers are 3.4 Angstroms apart. It is the fact that the layers are held together by weak Van der Waals forces that make graphite soft. Note each layer of graphite itself is quite strong - in fact graphene is nothing but one of these layers (i.e. one carbon atom thick layer).