Transcript Energy - PBworks

Energy
Carbon
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Atomic number : 6
Group: IV
Most common isotope: C12
Electron configuration: 2,4
Bonding: covalent
Allotropes
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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
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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
Dispersion forces
Graphite
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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:
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Single bonds eg: methane
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Double bonds eg: ethene
Bonding in carbon compounds
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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
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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
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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)
Alkanes
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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
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
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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
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Alkenes containing more than 4 carbon atoms may
have different structures. For example:
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This is called structural isomerism.
Isomers have the same molecular formula but the
atoms in the molecule are arranged differently
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