 Now let's have a look at methane. First we draw the Lewis structure and then we look at the electronegativities. You can see that the CH bond is only very slightly polar. In fact people sometimes classify these types of bonds where the difference in electronegativities is very slight as non-polar but I like to make the distinction between truly non-polar bonds and only slightly polar ones. So now we draw in the bond dipoles and carbon is the more electronegativ atoms. So all four dipoles have the same magnitude and they're all pointing inward along the four bonds towards the central carbon. And now we have to add them together to find the overall molecular dipole. Now working out how the dipoles sum in a tetrahedral molecule takes some thinking about but it's not necessary for this course for you to be able to do it rigorously. If you go through and do it properly and you really just need basic trigonometry for this you'll find that the three bottom vectors sum to give a dipole that points upwards like this which happens to point in exactly the opposite direction and be exactly equal in magnitude to the top vector which is pointing down. So overall these four bond dipoles cancel out and methane is a non-polar molecule. This is a good shortcut to keep in mind. In a tetrahedral molecule if the dipoles are all the same magnitude they will cancel out. If they're not all the same magnitude then you may need to think more carefully about how they will sum but you can usually make a fairly good estimate without getting too involved in the trigonometry.