COCl2 is also called phosgene. First we need to count the total number of valence electron. We just add the valence electron of each atom involved.

C = 4

O = 6

Cl = 7 x 2

------------

        24 electrons

Next, we have to assign the central atom; In this case it is C.

Now we have to connect the atoms and form a bond. We have now C=O, and two C-Cl bonds

      O

      ||

      C

   /     \

Cl        Cl

Finally, we have to distribute The remaining electrons on Cl and O. Remember the octet rule. COCl2 forms a trigonal planar and has an angle of approximately 120 degrees.