# Understand The Background Of Lewis Structures

0
10

Nuclear chemist John Peters was the first to use Lewis structures as a way of representing molecules with two atoms in 1922. It can be difficult to abstractly visualize how interactions between different atoms affect many molecules, but a Lewis Structure diagram shows you what is happening between all of these interactions. Decide whether these proposed lewis structures are reasonable or not and write your own Lewis structure. In the first Lewis structure, you can see that each carbon has a single bond to nitrogen and there are three bonds between each hydrogen. Because the three bonds between each hydrogen are the same length, they are geometric isomers which means they will have the same molecular formula but different molecular structures.

In this case, both forms of carbon dioxide will have a similar molecular formula of CO2 however they will have two different forms of molecular structure. In the second Lewis structure, you can see that each carbon has two hydrogen bonds, but there are still three bonds between each hydrogen. In this case, both forms of carbon dioxide will have the same molecular formula and different molecular structures.

The third Lewis structure shows that each carbon atom has a single bond to nitrogen and there are four bonds between each hydrogen.  In this case, both forms of carbon dioxide will have similar molecular formulas and different molecular structures because lewis structures are not fixed for all molecules. The final order always follows Hückel’s rule: if the bond order is one less than the number of atoms in a molecule minus two then the molecule has two forms of atomic coordination.

Understand The Background Of Lewis Structures :

## 1. Lewis structures are used to show the interactions between electrons in a molecule.

These are called electron pairs and are symbolized by two dots between atoms. The distance between these dots is very small and does not represent a real physical bond. When writing Lewis structures for CCl4, you can use four single bonds to represent the double covalent bond that makes up a carbon-to-carbon bond. When writing lewis structures, all bonds are assumed to be the same length unless otherwise noted with angle brackets like this: ( ). This means that all bonds shown in a lewis structure have equal length and they form an average bond angle of 109 degrees between them.

## 2. Lewis structures are used to show the geometrical isomers that can result from certain changes in a molecule.

If you change the relative lengths of any of these bonds, you can get a new geometric isomer. In lewis structures, if you change only one bond length, you will still get the same geometrical isomer. This means that all geometrical isomers are obtained by changing one bond length. To make lewis structures for molecules with more than two atoms, simply draw new bonds between all atoms! This usually involves drawing more bonds between each atom than in the original molecules.

## 3. Knowing how to read Lewis structures can be very useful when trying to predict the number of new geometric isomers a molecule will make.

Just like any other molecule, a molecule may have more than one geometrical isomer. How many different geometric isomers the molecule will make depends on how many bonds are changed in a lewis structure. If you change all bond lengths by one unit, then the result is called an enol tautomer and it has two different forms of molecular structure with the same atomic formula. If you change only one bond length, you get a mixture of two geometrical isomers. For example, CH2=CH-CH3 has one enol tautomer and four possible isomers called ketals. On the other hand, CH2=CH-CH2=C-H2 has ten different geometrical isomers but only one enol tautomer.

## 4. Lewis structures are not fixed structures but can be changed to represent any molecule.

Lewis structures are not one unique structure that fits every molecule but no matter how many bonds you add, the atomic formula will remain the same because these new bonds do not affect the atomic number of atoms in a molecule. If you only add a single bond to the molecule, you will have one molecule with one geometrical isomer. If you add two bonds to the molecule, then you will have two molecules with different geometrical isomers. If you add three bonds, then your Lewis structure will have three different geometric isomers and so on.

## 5. You can write Lewis structures for any molecule if you understand how to do so using Hückel’s rule and the number of bonds in a molecule minus two.

Lewis structures are not fixed rules that fit all molecules but they are instead rules that apply only to certain groups of molecules. The general rule is this: if the bond order is one less than the number of atoms minus two, then your geometric isomer will have a different atomic formula. In other words, if you add one bond, your geometric isomer will have an alternate form of molecular structure and if you add two bonds, you will have another two molecules with a different molecular structure.