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Writing Molecular Formulae
A molecular formula
shows the kind and number of atoms in a molecule
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Examples of Molecular Formulae of Some Common Compounds |
|
Common name |
Molecular
Formula |
Carbon |
Hydrogen |
Oxygen |
Nitrogen |
|
Water |
H2O |
0 |
2 |
1 |
0 |
|
Carbon dioxide |
CO2 |
1 |
0 |
2 |
0 |
|
Ammonia |
NH3 |
0 |
3 |
0 |
1 |
|
Vinegar |
CH3COOH |
2 |
4 |
2 |
0 |
|
Table sugar |
C12H22O11 |
12 |
22 |
11 |
0 |
Drawing Pictures of Molecules
In spite of the fact that molecules are far too small to
be seen, we have several ways of drawing pictures of them. Scientists
frequently draw diagrams called structural
formulae to illustrate how the atoms are
arranged in a molecule.
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Structural Formulae of Some Familiar
Molecules |
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Water |
H—O—H |
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Carbon dioxide |
O—C—O |
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Ammonia
|
 |
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Vinegar |
|
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Sucrose
(table sugar) |
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Three Dimensional Molecular Models
The
structural formulae of macromolecules are often so complex that they can’t be
drawn in two dimensions. Early pioneers of molecular biology build models from
wood, wired and other materials. With the advance of computer graphics,
however, three dimensional models that represent
their structure and shape can be created. Often these take the form of
stick and ball models in
which atoms of different kinds are represented by colored balls with the bonds
connecting them represented by sticks. Such models are extremely useful in
understanding the functions and interactions of the large molecules found in
living cells (as long as you don't think this is really what they look like;)
A ball and stick model of an unidentified protein
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