Lewis Structures

[Claudeth Martinez 1D]

hey,

Does anyone know how I can use Lewis structures to determine if a molecule is polar or nonpolar?

[Haowen_Liang_3E]

if you set up the Lewis structure correctly, and know your electronegativity, then you can figure which molecule keeps the shared e- longer (more negative). Then look at the angles and placement of those charged regions, if the charge molecules are skewed to one side, or not balanced with another charged molecule on the opposite side, then it is polar.

[Laura Gong 3H]

One easy way too tell if a molecule is non polar is if the atoms surrounding the central atom are all the same. For example CH4 is non polar.
Granted if there is a lone pair on the central atom and the atoms are the same around it, it will actually polar. For example, SO2.

[Brian Chang 2H]

Polarity is often linked with Symmetry.

CH4 is a tetrahedral molecule so it's charge is nicely balanced out between the 4 H atoms.

But H2O is bent because Oxygen has 2 bonding pairs and two lone pairs. So the lone side of the molecule is more negatively charged than the side with Hydrogen atoms. So it's a polar molecule.

This is also the explanation for the cohesion of water molecules.

Cheers.