How to draw lewis structures For Any Molecule | Examples For SiCl2Br2, PH3, NH4

Lewis was the first to describe the structure of simple molecules on the bases of valence electrons. He was successful in his initial experiments, but later on some new models and theories were published for more accurate structure even for complex molecules.
Lewis structure is the simple figure showing covalent bond and valence lone pair of electrons. It is very simple and easy process to draw lewis structure. First, apprehend the concept and practice it several time, until you have grip over it.
This is the Lewis structure for a water molecule.

Lets start !!! Before Each Step, look at the Picture above, It will help you a lot. 

Step By Step Process Of drawing a Lewis Structure:

Step 1:

Count the valence electrons for each atom making up a molecule. Valence electrons are the key that give you an idea about the structure. In other words one can say lewis structure is the game of valance electrons or more precisely a game of lone pair of electrons. Lone pairs are those electrons which dont take part in bonding so we called them as lone pairs of electrons. 

Step 2:

Complete the octed rule for every atom participating in the molecule. Octed rule is just gaining of noble atomic configuration. Share electrons with the neighboring atoms and show it through some dots pointing toward each other. This is the first step, complete it and then you will be able to move ahead for further completion of the structure as by lewis.

Step 3:

Now draw lines toward each other as per covalent bond. Number of lines equals number of bonds need to complete octed.

Step 4:

Show non-bonding electrons as a pair or more accurately as lone pair at one side. Non bonding electrons act in a pair thats why show them as lone pairs side wise. 

step 5:

Now Choose up a central atom. It is not difficult to judge central atom. Just look at the valency, one having greater valency then all of other will be declared as central atom. Whole structure is build around a central atom.
This completes the lewis structure for water and you can try it on all the other ones

Structures Of Some Important Molecules Like SiCl2Br2, PH3, NH4

SiCL2Br2 Lewis structure draw with Dots

Lewis Structure For PH3 molecule

Lewis structure For NH4: