Appearance
The expected similarity in appearence bewteen elements in the same Group is much less apparent in Group 4, where there is a considerable change in character on descending the Group. Carbon is a dull black colour in the form of Graphite, or hard and transparent in the form of Diamond; Silicon and Germanium are dull grey or black; Tin and Lead are shiny grey in colour.

General Reactivity
In Group 4 the elements change from non-metallic in character at the top of the Group to metallic at the bottom. Carbon is a non-metal, Silicon and Germanium are metalloids, and Tin and Lead are typical metals. The general reactivity of the Group as a whole is difficult to ascertain, and the reactivity of the elements must be considered individually.

Occurrence and Extraction
Carbon, Tin and Lead can all be found in the elemental form in the Earth's crust, and are readily mined.

Silicon is found in mineral deposits and purified from them. Very pure Silicon is required for semi-conductors, and is obtained from Silicon (IV) chloride.

Physical Properties
The physical properties of Group 4 elements vary quite widely from one element to another, consistent with the increasing metallic character on descending the Group. The structures change from giant molecular lattices in Carbon and Silicon to giant metallic lattices in Tin and Lead, which gives rise to the changes in physical properties. The change in bonding from covalent to metallic down the Group causes a decrease in melting point and boiling point. At the same time, the increasing metallic characteristic causes an increase in density and electrical conductivity.

Diamond has a high refractive index, the reason for its sparkle, and this combined with its rarity has made it valuable as a jewel. It is also the hardest known natural substance, and so is important industrially.

The most important physical property of Silicon and Germanium is that they are semi-conuctors, and have revolutionised the computer and microprocessor industries.

Tin and Lead, as typical metals, are relatively good conductors of electricity.

Chemical Properties
In general, chemical reactivity inceases on descending the Group.

Carbon is strikingly different from the other elements of the Group as it has the unique ability to form stable compounds containing long chains and rings of Carbon atoms. This property, called catenation, results in Carbon forming a huge range of organic compounds. The ability to catenate is due to the fact that the C - C bond has almost the same bond energy as the C - O bond, so that the oxidation of Carbon compounds is energetically favourable. Also, the small size of Carbon atoms allows two Carbon atoms to form multiple bonds. C - C and C - Si bond energies are very similar, so many organo-Silicon compounds are known. Silicon, however, does not form multiple bonds.

Silicon is unreactive chemically because an oxide layer seals the surface from attack, and high temperatures are required for oxidation to occur. Silicon does, however, react with Fluorine at room temperature. It is not attacked by aqueous acids, but does react with concentrated alkalis.

Tin and Lead are quite easily oxidised, Tin usually to Tin (IV) oxide and Lead to Lead (II) oxide. Both Tin and Lead reduce the Halogens.

Oxides
There are many oxides of Group 4 elements. The major oxides are:

CO(g)
CO2(g)
SiO2(s)
SnO(s)
SnO2(s)
PbO(s)
Pb3O4(s)
PbO2(s)

Oxides with a lower oxidation number become more stable going down the Group.

Carbon dioxide is the essential source of Carbon for plants. During photosynthesis Carbon is combined with water to form carbohydrates. Solid Carbon dioxide sublimes directly to a gas, and so is used as a cheap refrigerant.

Silicon forms a strong bond with Oxygen in Silica, SiO2, one form of which is Quartz. Sand is impure Quartz. Oxoanions derived from Silica are called Silicates. They are very common and have structures based on SiO4 tetrahedra. One of these is Asbestos.

Tin (IV) oxide, Tin (II) oxide and Lead(II) oxide are amphoteric.

Halides
All the elements of Group4 form tetrahalides, but only Tin and Lead form dihalides. The tetrahalides are covalent tetrahedral molecules whereas the dihalides are best regarded as ionic.

Hydrides
The hydrides of Carbon are the hydrocarbons - organic compounds.

Silicon forms a series of hydrides called the Silanes, with the general formula SinH2n+2.