Question

Using an arrow,indicate the direction of polarity on all covalent bonds. Predict ,which molecules are polar and show the direction of dipole moment (a)CH3Cl (b)SO3 (c)PCl3 (d)NCl3 (d)CO2?

Answer 1

a) dipol moment from the H- atoms towards the cl- atom.
b) symmetric atom -> non polar
c) dipol moment towards the cl-atoms
d) towards cl-atoms.
e) symmetric --> non polar

Explanation:

Step 1: Write Lewis structure.

Step 2: is the molecule symmetrical or not?

Symmetrical molecules have the same distributing of Electrons around the Whole atom. Allowing the atom to have the same charge everywhere. (it is not negativ at one side, and positiv at another)

Conclution: symmetrical atoms are non polar

Lets take a closer look at the polar molecules:
Step 3: Which way does the dipol moment work?

Take a look at the Lewis stucture of the molecule.
Example c)

(dont know why the Picture is so huge... lol)

There are a lot more Electrons around the cl. Therefore, the molecule is more negative around the cl-atoms.
The Arrow will therefore point towards the cl-atoms.

Hope this answer is helpfull!
Good Luck :)