How to know if it's Polar or Nonpolar?

I understand the molecular geometry to figure out the shapes, and I get the Lewis Dot Structures, but Im having a bit of trouble figuring out whether the molecules are polar or nonpolar(sorry if it’s a stupid question). Here’s some examples of molecules; can you tell me how you figured out if they were polar or nonpolar?

1. SF2

2. CH2O

3.CH2Cl2

4. O2

5.NO2^-1

✅ Answers

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I’ve been having the same problem as you, but i’ve been studying really hard for my exam (tomorrow) so i think i’ve got it now.

1. SF2-Polar. When you draw its lewis structure you’d think it was non polar because its symmetrical. However, the lone pairs apply pressure on the bonds changing its shape to bent. Just lie H20.

2. CH20(formaldehyde) – Polar again. Its not symmetrical so it has to be polar.

3. CH2Cl2- Non-polar. If you draw it out, you will have 2 Chlorides and 2 Hydrogens attaching to the Carbon. And since its tetrahedral it is symmetrical. So its non-polar.

4. O2- Non-polar. If you ever see two of the same atoms together then they are non-polar. they cancel each other out. Polarity is based on electronegativity.

5. NO2}-1 – Drawing the lewis structure you’ll notice that this is a resonance structure. So it cant be symmetrical. So its Polar

Summary: Symmetrical-Non Polar

Asymmetrical (Non-symmetrical) – Polar

PS- for molecules with three bonds coming out from each direction…ex:BF3 they are usually considered symetrical. Unless the central atom has a lone pair. In which case the become non-symmetrical.