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All the elements of Group 14 form covalent hydrides. Carbon forms a very large number of compounds which include alkanes (CnH2n+2), alkenes (CnH2n), alkynes (CnH2n-2) and aromatic compounds.
Silicon forms a limited number of saturated hydrides (SinH2n+2) called silanes, which are strong reducing agents. One of the methods used in the preparation of silanes is by the reduction of silane halides by LiAlH4, LiH or NaH.
SiCl4 + LiAlH4 SiH4 + AlCl3 + LiCl
Si2Cl6 + 6LiH Si2H6 + 6LiCl
Si3Cl8 + 8NaH Si3H8 + 8NaCl

Silanes are easily hydrolyzed in alkaline medium.
Si2H6 + (4 + n) H2O 2 SiO2   nH2O + 7H2.

Germanium hydrides (also called germanes) are similar to silanes but are less inflammable.
Stannane (SnH4) and plumbane (PbH4) are also known but are less stable.


All the elements of Group 14 form tetrahalides with the exception of PbI4 which is not known. Probably, this is due to the fact that PbIV is a strong oxidizing agent and I- is a strong reducing agent, so both strong oxidizing and reducing agents cannot exist together. They are all covalent and volatile with the exceptions of SnF4 and PbF4, which have three-dimensional structures and are high melting.

The stability of the halides decreases down the group. CCl4 is stable while other halides are hydrolyzed due to the availability of d orbitals. The hydrolysis of SiCl4 may be represented as follows.

The hydrolysis of SiF4 besides producing SiO2 also produces [SiF6]2-
SiF4 + 2H2O SiO2 + 4HF


The elements of Group 14 form oxides of the type MO and MO2. The well-known oxides of carbon are CO and CO2. Besides these, less stable C3O2, C5O2 and C12O9 are also known.

Carbon monoxide is extremely poisonous gas. If inhaled, it forms a complex with haemoglobin in the blood which is much more stable than oxy-haemoglobin complex. This prevents the haemoglobin in the red blood corpuscles from carrying oxygen around the body. This causes an oxygen deficiency, which could be a fatal to life.

CO is a good reducing agent. It is also an important ligand which can donate or share a lone pair of electrons located on carbon atom.

Carbon dioxide is a colourless, odourless gas, which plays a vital role in photosynthesis. Carbon dioxide is represented as O = C = O. Each double bond involves one σ bond and one π bond. The formation π bonds is possible because of the small size of carbon and thus the overlapping between 2p(C) and 2p(O) are possible. Because of the double bonds, CO2 exists as discrete molecule and is a gas.

Silicon also forms silicon dioxide, which is a solid and has a high melting. Silicon is not able to form pp-pp double bonds with oxygen due to its large size which prevents effective overlap between 2p(Si) and 2p(O) orbitals. Instead, a continuous chain of stronger Si—O bonds exist in silicon dioxide giving an infinite three-dimensional structure. Each silicon is bound tetrahedrally to four oxygen atoms and two silicon atoms share each oxygen atom, as shown in Fig. 10.26.
SiF4 + 2F- [SiF6]2-
Acidic nature of the dioxides decreases down the group.
CO2 and SiO2 are purely acidic.
GeO2 is weakly acidic.
SnO2 and PbO2 are amphoteric.
The lower oxides GeO, SnO and PbO are also known. They are slightly more basic and ionic than the corresponding higher oxides.
GeO is purely acidic
SnO and PbO are amphoteric.
The stability of lower oxide increases down the group.
Lead also forms a mixed oxide 2PbO  PbO2 (i.e. Pb3O4). It is used as red pigment.


The earth's crystal rocks and their breakdown products like clays, soils and sands, are mostly silicates and silica. Mica, asbestos, quartz, feldspar, zeolites, etc. are some of the important silicate minerals. Basically, all the silicates and silica contain SiO4 tetrahedra. They differ only in the way the tetrahedra are linked together.


Silicones form a group of organosilicon polymers of wide commercial use. They have general formula (R2SiO)n, where R may be methyl, ethyl or phenyl group.

For the straight-chain polymer, dimethyldichlorosilane (CH3)2SiCl2 is used. Its hydrolysis followed by polymerization may be represented as follows

The above reaction continues because of active OH group at each end of the chain.


Hydrolysis under controlled conditions can produce cyclic structures with rings containing three, four, five or six Si atoms.

Trimethylmonochlorosilane (CH3)3SiCl can be used to block the polymerization as it does not create the active OH group at the end of the chain.

The hydrolysis of methyltrichlorosilane RSiCl3 produces a very complex cross-linked polymer.

The durability and inertness of silicones is due to the silica-like arrangement Si—O—Si—O—Si which involves very strong Si—O bonds with bond enthalpy 502 kJ mol-1. The Si—C bond is also very strong.

Silicones are used in waterproofing textiles, in glassware, as lubricants and as anti-foaming agents. Silicon rubbers are excellent electrical insulators. Silicon resins are used in paints and varnishes.

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