Polarity and positioning of atoms in Lewis Structures

[Shirley Liu 2I]

When finding the polarity of a molecule, we have to first draw the Lewis Structure of the molecule and then draw dipoles depending on the electronegativity difference between the central and outer atoms. However, wouldn't the position of the outer atoms matter, especially if they are different from each other? Wouldn't they be pulling the electrons in a different direction depending on the atom and the position of them in relation to the central atom, such as in a tetrahedral shaped molecule? Or does position of the different atoms around the central atom not matter?

[Andrew Bennecke]

In a nonpolar Lewis Structure with a tetrahedral shape (CH4), we draw just as we have been drawing it since the dipoles cancel and each of the terminal atoms provide equal repulsion unto the central atom. However, in a Polar Lewis structure with a tetrahedral shape (CClH3), we should draw the structure with a slight variation in bond angle away from the polar atom or away from the lone pair of electrons, such as in NH3 (Shape changes to Trigonal Pyramidal).

[Ronak Singh]

The position of atoms around the central atom doesn't matter because all of the bond angles are the same.