Energy

Carbon Atomic number : 6 Group: IV Most common isotope: C12 Electron configuration: 2,4 Bonding: covalent

Allotropes Allotropes are forms of the same element (in the same physical state) which have distinctly different physical properties (eg: colour, density, hardness) Diamond and graphite are allotropes of carbon. Allotropes have different physical properties because the atoms are joined in different ways to form molecules or crystals

Diamond Covalent network structure Carbon atoms are arranged in the shape of a tetrahedron One carbon atom in the centre surrounded by four other carbon atoms Each carbon atom shares a pair of electrons with four other carbon atoms Covalent bonds

Graphite Carbon atoms are arranged in flat parallel layers. Dispersion forces Carbon atoms are arranged in flat parallel layers. Each carbon atom is covalently bonded to three other atoms forming hexagonal rings The fourth electron is delocalised The strong covalent bonds hold the carbon atoms together in the rings, however, bonding between layers is relatively weak and consists of dispersion forces http://www.everyscience.com/Chemistry/Inorganic/Carbon/a.1189.php

Bonding in carbon compounds In organic compounds carbon atoms almost always form four bonds. These may be: Single bonds eg: methane Double bonds eg: ethene

Bonding in carbon compounds Triple bonds eg: ethyne

Representing structures The bonding and structure of carbon compounds can be represented by ball and stick, electron dot diagrams, structural formula etc. The following diagram represents the three dimensional structure of the compounds.

Hydrocarbons Compounds that contain only carbon and hydrogen. Aliphatic hydrocarbons have either straight chain or branched chain structures and include: - alkanes: all the bonds are single bonds - alkenes: contain a carbon-carbon double bond - alkynes: contain a carbon-carbon triple bond

Nomenclature The name for a carbon compound consists of a stem which tells us the number of carbon atoms in the chain and a suffix that tells us the family the compound belongs to (alkane, alkene, alkyne)

What are the names and formula of each of these alkanes? When naming take the usual stem name to indicate the number of carbon atoms in the chain and then add the suffix ‘ane’ Structural formula CnH2n+2 What are the names and formula of each of these alkanes?

Alkenes Structural formula CnH2n When naming: 1. Take the usual stem name to indicate the number of carbon atoms in the chain and then add the suffix ‘ene’ 2. Show the location of the double bond by putting in front of the name the number of the carbon atom at which the double bond starts 3. Begin numbering the carbon chain from the end of the molecule that minimises the number for the double bond Structural formula CnH2n

Example 1. Number of atoms in the chain = 4 therefore the stem name is ‘but’ 2. Putting in front of the name the number of the carbon atom at which the double bond starts – remembering to begin numbering the carbon chain from the end of the molecule that minimises the number for the double bond Start numbering at this end

Isomers Alkenes containing more than 4 carbon atoms may have different structures. For example: This is called structural isomerism. Isomers have the same molecular formula but the atoms in the molecule are arranged differently