Carbon have two types of Allotropic forms

(i) Crystalline

(ii) Amorphus

Diamond, Graphite and Fullerene

(A) Diamond :

(a) Each carbon is linked to another atom and so very closed packing in structure of Diamond.

(b) Density and hardness is very much greater for diamond because of closed packing in diamond due to `sp^3` hybrid and are tetrahedrally arranged around it.

(c) Diamond has sharp cutting edges that's why it is employed in cutting of glass.

(d) Diamond crystals are non conductor of electricity because of not presence of mobile electron.

(e) `1` carat of diamond = `200` mgm.

(f) Diamond powder if consumed is fatal and causes death in minutes.

(B) Graphite :

(a) In graphite carbon are `sp^2` hybridised and due to this carbon exist as hexagonal layer.

(b) Each carbon is lined with `3` carbons and one carbon will be left and form a two dimensional shed Iike structure.

(c) Distance between two layers is very large so no regular bond is formed between two layers. The layers are attached with weak van der Waal force of attraction.

(d) The carbon have unpaired electron so graphite is a good conductor of current.

(e) `C-C` bond length in Graphite is shorter (`1.42` `A^o`) than that of Diamond (`1.54` `A^o`).

(f) Graphite has high melting point so it is employed in manufacture of crucible.

(g) Graphite when heated with oxidising agents like alkaline `KMnO_4` forms metallic acid. See fig.1.

(C) Buck Minster Fullerene :

(a) It has the formula `C_(60)` and is made from interlocking hexagonal and pentagonal rings of carbon atoms.

(b) Such molecules are now thought to exist even in chimney root or candle smoke.

(c) The structure of `C_(60)` is similar to the surface of a football which has also set of interlocking hexagons and pentagons.

(d) Another molecu le `C_(70)` has been recently discovered.

(e) These and similar large carbon molecules are sometimes referred as "bucky balls

(A) Lamp Black :

(i) Obtained by incompletely combustion of compounds which contains higher `%` of carbon, benzene, turpentine, acetylene etc. These all on combustion form black carbon called lamp black.

(ii) Black blue ink, printing ink, black paints, varnishes are made from lamp black.

(B) Coke :

(i) Obtained by destructive distillation of coal.

(ii) Coke is usually employed as weak reducing agent with compared to `CO`.

(C) Wood Charcoal

(i) Obtained by incomplete combustion of wood.

(ii) Used to decolourise organic compound.

(i) It has three allotropic forms

(a) White tin :

`=>` Used in containers of oil.

`=>` White tin is more stable and having maximum density.

(b) Grey tin :

(c) Rhombic tin :

(ii) At low temp. `(18^oC)` white tin converts to Grey tin.

(iii) At temp. of 1`60^oC` (above) white tin converts to Rhombic tin.

(iv) White tin forms grey tin which is obtained as powdery substance and with formation of this thickness of white tin container decreases. This is called Tin pest or Tin disease or Tin plague.

(v) When tin sheets are folded, they give a peculiar sound which is called as Tin cry.

The property of forming bonds with atoms of the same element or tendency to self-linking called catenation. Carbon shows maximum catenation. On moving down the group catenation tendency decreases. This is because the strength of `C-C` bond is very high and in case of other elements, strength of `M-M` (where `M = Si`, `Ge`, `Sn`, `Pb`) bond is decreases down the group.