Lewis Dot Structure

Lewis Dot Structure

The Lewis Dot Structure rare atoms from networks of covalent bonds. 

Drawing the Lewis Dot Structure

Drawing the Lewis Dot Structure, will represent the atom’s chemical bond. 

In this case I’ll be demonstrating what to do with Carbon (C) 

First I’ll find the chemical symbol which is C. Then I’ll place it’s valence electrons around it. You can determine the amount of valence electrons from counting left to right on the Periodic Table of Elements until you get to Carbon. Doing this, you’ll count over spaces therefore there are 4 valence electrons. 

All atoms have 4 cardinal sites which can create bonds with electrons; this is how it fills its octet or outer most shell. When we draw the valence electrons, we put them around the symbol not pair them up until we have to. 

When elements are in the same group they will have similar looking Lewis Dot Structure because they have the same amount electrons. 

Drawing Lewis Dot Structure for a molecule 

The example we will be working with is HCL.

To draw the Lewis Dot Structure for a molecule we’ll start off by drawing each atom separately with its valence electrons.

Then we will pair the single electrons together in. The two dots in the covalent bond will become line. The covalent bond will always contain two electrons. 

The electrons need to be paired. The electrons that aren’t in a bond are called lone pairs. Any good Lewis Dot Structure will be in a covalent bond or in a lone pair.

The number of valence electrons an atom has determines how many bonds it can form. Carbon can make 4 covalent bonds and it has no lone pairs. Nitrogen can make 3 covalent bonds and it will have 1 lone pair. Oxygen has 2 covalent bonds and it has 2 lone pairs. Florine has 1 covalent bond and it has3 lone pairs

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Atoms can have double or triple bonds. When two atoms have only one covalent bond between them it is called a sigma bond. 

For Example, carbon dioxide or CO2.

We have to make a sigma bond but there will still be unpaired electrons. The unpaired electrons will make mother covalent bond. The second covalent bond is called a pi bond. 

 3 covalent bonds don’t have a name. You say 1 sigma and 2 pi bonds.

Sometimes atoms will have a formal charge. This happens when the number of electrons an atom contributes to the Lewis Dot Structure is different from its normal valence. 

Nitrogen for example has 5 valence electrons. When ammonia contributes to those 5, nitrogen will become a neutral atom. For ammonium ion, nitrogen would be contributing 4 electrons to the Lewis Dot Structure (one per bond). It is less than its typical valence meaning it will have a formal positive charge making it a polyatomic ion. 

Filling the Octet or outer most shell

Carbon, Nitrogen , Oxygen , Florine all need 8 electrons to fill its octet or outer most shell but Hydrogen and helium need 2 to fill its octet or outer most shell because they are so small. Phosphorus and sulphate can have more than 8 electrons to fill its octet because they are so big.