Carbon (C), Silicon (Si), Germanium (Ge), Tin (Sn) and Lead (Pb) belong to group-14 of the periodic table. This group is also known as carbon family. A regular gradation of non metallic nature to metallic nature through semi-metallic nature is observed in this group. Carbon and Silicon are non metals, Germanium is a metalloid, whereas Tin and Lead are metals.
* The general outer electronic configuration of group-14 elements is: ns2np2.
* The atomic numbers, electronic configurations, corresponding periods and the chemical nature of these elements are tabulated below.
|Electronic configuration||Chemical nature|
|2||Carbon||C||6||[He] 2s2 2p2||Non metal|
|3||Silicon||Si||14||[Ne] 3s2 3p2||Semi metal (metalloid)|
|4||Germanium||Ge||32||[Ar] 3d10 4s2 4p2||Semi metal (metalloid)|
|5||Tin||Sn||50||[Kr] 4d10 5s2 5p2||Metal|
|6||Lead||Pb||82||[Xe] 4f14 5d10 6s2 6p2||Metal|
Since there are 4 electrons in the valence shell, they can make use of these electrons in the bond formation to get octet configuration. Hence their usual valency is 4.
However the group 14 elements other than carbon can also show the maximum valency 6 due to the presence of available d-orbitals in them. But carbons maximum valence is 4 due to non availability of d-orbitals.
Their usual stable oxidation number is +4. The negative oxidation numbers are also possible with carbon. It is also observed that the stable oxidation state of Sn and Pb is +2 rather than +4 due to "inert pair effect".
The atomic radius increases from top to bottom i.e., C to Pb.
The ionization energies, electron affinities and electronegativities decrease from top to bottom with increase in the atomic size.
Note: The IE of Lead is greater than that of Tin.
Therefore the metallic nature increases from C to Pb.
However due to comparatively smaller atomic and ionic sizes they usually tend to form covalent compounds. The first three elements i.e., C, Si & Ge form mostly the covalent compounds. However, the tendency to form covalent compounds decreases from C to Pb. The metals, Sn and Pb can form Sn2+ and Pb2+ ions easily.