The elements that follow carbon constitute the IV B group or the carbon family. They are carbon (C), silicon (Si), germanium (Ge), tin (Sn) and lead (Pb). Carbon forms the most important constituent of organic matter and introduces a new branch of chemistry known as organic chemistry.
Carbon and silicon are the most abundant elements in earths crust whereas germanium occurs only as traces. Tin and lead also occur in small amounts. Out of all these elements carbon and silicon are non metals, silicon also behaves as metalloid, Germanium is metalloid and Tin and Lead are metals.
Carbon Family Name
Do all Organic Compounds Contain Carbon?
The simplest organic compounds are hydrocarbons, compounds that contain only carbon and hydrogen. Hydrocarbons can be grouped into three categories:
- Alkanes - which contain only single carbon-carbon bonds.
- Alkenes - which contain carbon-carbon double bonds.
- Alkynes - which contain carbon-carbon triple bonds.
Carbon compounds form 95% of the total number of known chemical compounds. Most carbon compounds contain large quantities of hydrogen. The molecular structure of humans is based of organic compounds. Examples are proteins, lipids and carbohydrates. Most pharmacological substance and all plastics also contain carbon.
Uses of CarbonBack to Top
What are the Uses of Carbon?
Some common uses of carbon are given below.
- Carbon is an excellent reducing because it readily combines with oxygen to form CO and CO2. Thus in the form of coke in blast furnaces, it purifies metals by removing the oxides and other impurities from iron.
- Carbon as graphite has strong electrical conductivity properties. It is important component in electrodes used in a variety of devices, including flashlight cells (batteries).
- Amorphous carbon has some super conduction capabilities.
- Graphite is used for the "lead" in pencils as a dry lubricant and as electrodes in arc lamps. Also carbon is a popular jewelry item. (eg. Diamonds)
- Carbon is used in the form of fullerenes and applications of nano technology will provide many new and improved products with unusual properties.
Physical Properties of CarbonBack to Top
- Ionization potential - The ionization potential of IV B group decreases on descending the group. The ionization potential of silicon indicates that it is capable of forming positive ions more easily than carbon but it forms mainly covalent compounds.
- Electronegativity - Carbon is the most electronegative element of the family. The electronegativity values for Si, Ge, Sn and Pb are same (1.8) for all the elements.
- Catenation - Catenation is the property of formation of chains to form many chain compounds. Carbon can form even multimillion atom catenation compounds. Because of the high bond energy the C-C bonds are very strong in these homo polar compounds in comparison to Si-Si bond.
- Allotropy - All the elements of the family exhibit the characteristic property of allotropy or polymorphism. Carbon forms two type of allotrope, crystalline and amorphous. The crystalline allotrope of carbon are diamond and graphite.
Chemical Properties of CarbonBack to Top
- Hydrides - Carbon forms large number of hydride that is alkanes, alkenes, alkynes, dienes, polyenes, alicyclic and aromatic hydrocarbons. Other elements also form hydride such as silanes, germanes, stannane and plumbane. The reducing character of these hydride increases down the group.
- Oxides - Elements of group 14 form two types of oxide in general monoxides (MO) and dioxides (MO2). Monoxides: All elements form monoxides CO, SiO, GeO, SnO, PbO. Due to the presence of lone pairs CO can act as ligand and forms metal carbonyl like Ni(CO)4, Fe(CO)5 etc. Dioxides: Dioxides of these elements have general formula MO2. CO2 are weak acids while other are amphoteric. CO2 is monomeric, linear molecule with C atom in sp hybrid. Solid CO2 is called dry ice.
- Halides - These elements form halides with general formula MX4. Some of these elements form dihalides.
- Carbides - These are the compounds of carbon with other elements. The carbides are of three types. Ionic or salt like carbides, covalent carbides and interstitial carbides.
- Silicates - It is the general term given to solids with Si-O bonds. some examples are quartz, Asbestos and Feldspar and zeolites. Silicates are complex network solids having silicate (SiO4)4-.
Electronic Configuration of CarbonBack to Top
In general the outer shell electronic configuration for carbon family is ns2np2.
Carbon Family CharacteristicsBack to Top
- Atomic radii - Atomic radii increases down the group due to progressive addition of new energy shell. The magnitude of increase of radii decreases from Si onward due to improper shielding of d and f orbitals.
- Melting and boiling points - Melting and boiling points are higher than those of elements of group 13.
- Density - There is increase in the density of these elements from C to Pb.
- Metallic character - These elements are less metallic due to large values of ionization energies. In moving down the group the metallic character increases from C to Pb.
- Oxidation states - All elements show oxidation state of +4. On going down the group the tendency of +4 oxidation state decreases and that of +2 oxidation state increases. This is due to inert pair effect.
- Nature of bonding - Carbon shows the ability of p$\pi$-p$\pi$ multiple bonding because of its small size. The d$\pi$-p$\pi$ multiple bond is shown particular by Si and also by other elements to some extent.
Carbon Family Periodic TableBack to Top
Carbon Family UsesBack to Top
- Carbon nature allows the formation of rings and straight and branched chains of compounds that are capable of adding hydrogen as well as many different types of elemental atoms to these structures.
- Silicon is used in clays, silica sand and most kinds of building stone and it is a important part of ceramic brick.
- Germanium is used as a semiconductor to make transistors, diodes and numerous types of computer chips. It is also used as a brazing alloy for producing infrared transmitting glass and other types of lenses and for producing synthetic garnets that have special magnetic properties.
- Tin is alloyed with many metals. It is added to lead to make low melting alloys for prevention sprinkler systems and easy melting solder. Tin also has been mixed with other metals for making castings for letter type in printing press.
- Lead is used in different ways in combination with other substances. Red lead is used in the manufacture of flint glass and paint. It is also used in bullets and solder. Lead glass is also used in lenses for cameras and optical instruments because lead glass lenses bend light much more than those made from other materials.
Carbon Family PropertiesBack to Top
- Atomic radii - On moving down the group atomic radii increases.
- Ionization enthalpy - On moving down the group ionization enthalpy decreases.
- Electronegativity - On moving down the group the electronegativity decreases.
- Oxidation states - All elements mainly show +2 and +4 oxidation states.
- Allotropy- All elements show allotropy except lead.
- Melting and boiling point - Values of melting point and boiling point of these elements are much more high compared to boron family. On moving down the group it decreases.
- Density - On moving down the group the density increases.