What is the bond polarity and molecular polarity for these molecular bonds?

Bond Polarity question!?

• Ok, This has been bothering me. I am in chemistry 1 and my teacher has taught me two different ideas. HF is a polar bond because F is more electronegative and so it will attract more electrons making it partial negative. This will make the bond polar. Now take H2S, for example. The electronegativities are slightly closer in number. However, but because S has a higher electronegativity, it will attract the electrons. Now my dilemma. Take SiCl4 for example. I know that O2 is nonpolar bond because there is an equal amount of electronegativity, which would cause an equal attraction of electrons. Therefore, bond polarity is not valid in this case. So in a sense the O2 cancels out. Although that's not what happens, that can be perceived. Like with a -5 N force and 5N force being pulled both ways in a tug of war, there will be no attraction to one certain side. But, because I am in chem 1, my teacher wanted to make it easier for my class. F, O, N, Cl are the most electronegative values. So like in O2 where you can simply cancel out because the electronegs are equal, in SiCl4, you can cancel out the 4 Cl's and just let it be nonpolar because the Cl's are thus not present anymore. However, Cl is more electronegative, so the polarity of the bond will be present...thus making it a polar bond. My teacher said both techniques in class..and for the sakes to make the idea easier..it's made my decision making abilities harder.. I finished taking a test and none of the molecules were like O2 or I2 where the electronegs would be the same. There was a column to identify the bond polarity. I just put 'polar' for all of them because i considered that because the molecules consisted of two different types of elements, one would inevitably have a higher electronegativity, which would result in an attraction of electrons to one side. So, my question is, does the value (or difference) of electronegativity matter to make a bond polar. Even this is unlikely but if there were two elements with a difference of electronegatvity of 0.00001, would the bond of that molecule be polar? please, I want a theroetical answer as in yes or no. Please do not give me like it is way too small. because if it takes a billion years for that electron to be attracted to the other side..it would still be 'polar' because there is a difference in electronegaativity. Sorry, I just a little thrown over because this test was 25% of my grade and she barely taught us and i was gonna ask her questions but she was absent that day too

• Answer:

  a small difference is still polar O2, I2 SiCl4 are non-polar because of symmetry