Drawing Lewis Structures

Example 1 - CCl4

Step 1 - Determine the total # of valence shell electrons (e1-) used.

C is in group 4, Cl is in group VII

((4x 1) + (7x4)) = 32 e1-

1 C atom in CCl4 4 Cl atoms in CCl4

Step 2 - Place the single atom of C in the centre and place the 4 Cl atoms around it.

C

Cl

ClCl

Cl

Step 3- Place a pair of electrons between each pair of atoms.

C

Cl

ClCl

Cl

Step 4 - Place 8 electrons around all non-central atoms.

C

Cl

ClCl

Cl

Step 5 - If there are any electrons left, place them, in pairs, around the central atom .Example - In the case of SI4 after going through steps 1 - 4 you get:

Step 1# of e1- is:6 x 1 + 4 x 7 = 34

Step 2

S II

II

Step3

Step4

Step 5

Step 6 - If the central atom is in group 4, 5, 6, 7 or 8 the octet rule (rule of 8) must be satisfied by moving electron pairs from non-central atoms to central atoms, creating double bonds in the process.Example - SO2

Step 1# of e1- is:6 x 1 + 6 x 2 = 18

Step 2 & 3

S OO

Step 4Step 5

Step 6

S OO

Draw Lewis Structures for the following:SO2, CBr4, H2S, PBr5, SBr4, SeI2, SiS2, ClBr5, AlI3, SeS3,