 Okay so let's try this out with a real molecule. We're going to try and work out the molecular dipole of water. So our first thing is we need to know, well we know that the formula of water is H2O. So we need to know the electronegativities of hydrogen and oxygen. So we go away and look them up. We find that hydrogen is 2.2 and oxygen is 3.44. So the next step is we say which atom has the greater electron density. And you can see that the more electronegative atom is oxygen. So it's going to be the one that has the greater electron density. If I show you a picture from the Molecules 360 database, you can actually see this. So the red remember represents a higher electron density and the blue represents a lower. We can also draw this using the ball and stick model also from the Molecules database, which shows the partial charges on the atom. So that you can see the water almost has a full negative charge and each of the hydrogens has about half a positive charge. So most of the electron density is definitely around the oxygen. Okay our next step is to draw the bond dipoles. So to do this we need to draw our Lewis structure. And then we draw the bond dipoles for each bond. So hydrogen is less electronegative so the arrow is going to start there and point towards the oxygen. The bond dipole is parallel to the bond. Since each bond is made of the same combination of atoms, the length of those two dipoles should be the same if I draw it perfectly. I can show you the picture from the Molecules database and you can see the gray arrows there that are representing those bond dipoles. Okay the last step is to sum those two bond dipoles and find out what the molecular dipole is. So we need to look at these two red arrows that we've got here and we need to sum them together. So if I translate them down here, there's the left hand one and then I'm going to move the right hand one so that it's head to tail with the first. It'll look something like that. If we now sum those two arrows together, we draw an arrow from the tail of one to the head of the other and we find that the sum of those two dipoles is a dipole that points straight up the page. So we can redraw our water molecule with its molecular dipole that points straight up the page like that and there's a representation from the database. You can see the thick orange arrow here represents the sum of the two bond dipoles.