Step 1: Find valence e- for all atoms. Add them together.
Si:4
F:7x4=28
Total=32
Step2: Find octet e- for each atom and add them together.
S:8
F:8x4=32
Total=40
Step3: Gives you bonding e-. Subtract step 1 total from step 2
40-32=8e-
Step 4: Find number of bonds by diving the number in step 3 by 2(because each bond is made of 2 e-)
8e-/2= 4 bond pairs
Step 5: Find the number of nonbonding (lone pairs) e-. Subtract step 3 number from step 1.
32-8= 24e-=12 lone pair
Use information from step 4 and 5 to draw the lewis structure.
Silicon goes in the centre.
Lewis dot structure of SiF4
Alternatively a dot method can be used to draw the lewis structure.
Calculate the total valence electrons in the molecule.
Si:4
F:7x4=28
Total=32
Put Silicon in center and arrange fluorine atoms on the sides.put a pair of electrons connecting each fluorine with oxygen and the remaining four electrons on fluotrine atoms.