Drawing a Lewis Structure
Lewis structure is the structure of a molecule in which dots are used to show the electron position around the atoms that make up the molecule.
In order to produce the Lewis structure of a molecule, there are certain steps one needs to follow (they are five (5) in number). Basically what I will do is to use the molecule methane (CH4) as example to show you how to draw the Lewis structure of any molecule.
In order to produce the Lewis structure of methane, the first step is to count and determine the total valence electron present in methane (or any molecule of interest). Methane is made up of carbon and hydrogen atoms (CH4). The valence of carbon is 4 and that of hydrogen is 1. Since we have four hydrogen atoms in methane, the total valence electron in methane will be:
4 for carbon+1×4 for hydrogen=8(for ...view middle of the document...
In the case of methane we will have something that looks like:
The dots signify electrons, which are in pairs. If we count the total, it should give us the value we calculated in the first step = 8.
The fourth step is to check for octet rule (meaning that each atom must have eight pairs of electrons – this rule does not work for hydrogen and some other atoms, thus we need to check for octet rule for carbon, hydrogen is supposed to have just one pair of electron). Checking the octet rule means counting the number of pair electrons around carbon to know if they are up to eight. If yes, it means that we have our final Lewis structure. If no, it takes is to step five. Looking at the second figure above, the octet rule is satisfied. This means that the final Lewis structure of methane is:
If octet rule is not satisfied, and more electrons remain to be shared, move one electron per bond per atom to make another bond. An example is given below for CO2 molecule:
Isomers in organic chemistry are compounds that have the same molecular formula but with different structural formulas.
(1) Pentane is isomer. Its molecular formula is: C5H12. Other compounds that have this same molecular formula are: 2-methylbutane and 2,2-dimethylpropane. These three compounds have different structural formulas (see below):
(2) 2-methylbutane is an isomer. See above, it is an isomer of Pentane.
(3) 2,3-dimethylbutane is an isomer of hexane. Their molecular formula is: C6H14. Their structural formulas are shown below:
CH3(CH2)4CH3 for hexane and CH3CH(CH3)CH(CH3)CH3 for 2,3-dimethylbutane.
(4) 2,2-dimethylpropane is an isomer of pentane. See above.
(5) 1-hexene is also an isomer. For further information consult the following site: http://webbook.nist.gov/cgi/cbook.cgi?ID=R97406
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