How do you know if a compound is predicted to be polar or non-polar?
Especially if they use imaginary elements as examples?
It's hard to do on this forum because I can't draw a picture. But I'll try.
To be polar we muct have a molecule that is NOT symmetrical in space AND it has polar bonds. Here are some examples.
You know you have a polar bond if the electronegativity (EN) between the two atoms is not the same; i.e., C is about 2.5 and Cl is about 3.5 so the C-Cl bond is polar. C-H bonds, H-O bonds, N-H bonds, etc are polar because the EN of the two elements is not the same. That;s 1/2 the story. Now let's look at CCl4. If you draw that out you have four C-Cl bonds and all four of those bonds are polar BUT the MOLECULE CCl4 is NOY a polar molecule BECAUSE the CCl4 molecule is arranged in space symmetrically so that the center of + charge cancels with the center of negative charge. You may see this better if you Google CCl4 and see the 3D spacing for the molecule. Likewise, H2O is a polar molecule. The best I can do in drawing it is this.
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:O:H
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H
So each O-H bond is polar AND it is NOT symmetrical; i.e., the O end is negative and somewhere between the H atoms is the + end. You see the center of the - and + are not at the same spot; therefore, the polarity is not canceled. Same way with NH3. You have 3 N-H polar bonds but the negative charge is on the N end and the + charge is somewhere on average of the H ends. CCl4 is not polar but CHCl3 is as is CH3Cl etc. By the way, that's how we know H2O is not a linear molecule; i.e., it is not H-O-H BECAUSE it has a dipole moment due to its polarity. Hope this helps. If you still have questions, please repost and make clear what you don't understand. Also, you can look at Google to see diagrams of how the molecules look in space.