Why do some molecules (like water) form polar bonds and others like carbon dioxide do not?
1 Answer
This is electronegativity
Explanation:
Electronegativity refers to how an element holds electrons in a bond. Elements like Fluorine and Chlorine are much more electronegative than others. When put into bonds these elements tend to hold on to electrons more. Kind of like a ball hog in sports. The oxygen holds more electorns so it must be calculated how far apart they will be. keep in mind that the space around the molecule is 3D. In water you get the bent shape because it is the farthest apart all of the electrons can be. 
The triangle on the bottom hydrogen represents the atom being pushed out at the view.
Carbon dioxide on the other hand has two electronegative molecules pulling the plane even. This is because on each side the oxygens are hogging the electrons and they already separated the most that they can be. this draws a singe axis that all of the atoms follow.
