. Group (Carbon group) elements: . . Occurrence: Carbon is found in the native form as graphite.
Coal, crude oil and carbonate rocks such as calcite, magnesite etc... contains large quantities of carbon in its combined form with other elements. Silicon occurs as silica (sand and quartz crystal). Silicate minerals and clay are other important sources for silicon.
- - - - . . Physical properties: Some of the physical properties of the group elements are listed below Table . Physical properties of group elements Property Carbon Silicon Germanium Tin Lead Physical state at K Solid Solid Solid Solid Solid Atomic Number Isotopes C, C, C Si, Si Ge, Ge Sn Pb Atomic Mass (g.mol - at K) .
Electronic configuration [He]2s 2p [Ne]3s 3p [Ar]3d 4s 4p [Kr]4d 5s 5p [Xe] 4f 5d 6s 6p Atomic radius (Å) . . . .
. Density (g.cm - at K) . . .
. . Melting point (K) Sublimes at Boiling point (K) . .
Tendency for catenation Catenation is an ability of an element to form chain of atoms. The following conditions are necessary for catenation. (i) valency of the element should be greater than or equal to two, (ii) element should have the ability to bond with itself (iii) the self bond must be as strong as its bond with other elements (iv) kinetic inertness of catenated compound towards other molecules. Carbon possesses all the above properties and forms a wide range of compounds with itself and with other elements such as H, O, N, S and halogens.
. . Allotropes of carbon Carbon exists in many allotropic forms. Graphite and diamond are the most common allotropes.
Other important allotropes are graphene, fullerenes and carbon nanotubes. Graphite is the most stable allotropic form of carbon at normal temperature and pressure. It is