In chemistry, a polar bond is a type of covalent bond between two atoms or more in which electrons are shared unequally. A covalent bond is the "strong" kind of bond that makes something into a molecule.
Electrons are negatively charged. If the two atoms share the electrons equally, then the negative charge is evenly spread out over the entire molecule, balanced out by the positive charges of the protons in the atoms' nuclei. This makes the entire molecule neutral - a non-polar bond, making a non-polar molecule. However, if one of the atoms is particularly greedy for electrons (called electronegativity), then its side of the bond will have more electrons. Therefore, that side of the bond will have a slightly negative charge, and the other side will have a slightly positive charge.
This is important because it turns the bond into a magnet with two poles. Because it acts like a magnet, if other bonds that are a lot like magnets are nearby, it will react to them.
When these polar bonds are positioned right, the entire molecule can act like a magnet. Water does this. You can see in the image below that the hydrogen (small and white) is positively charged and the oxygen (big and red) is negatively charged. This picture shows how the little water magnets line up with each other, in the same way that if you toss a bunch of little magnets into a box, they'll line up with each other.
This is one of the most basic and important differences between bonds (and the resulting molecules) in chemistry. This is a very easy behaviour to predict (because we know how electronegative all of the atoms in the periodic table are), and it creates an enormous difference in how the molecules behave.
Other pages[change | change source]
- Chemical polarity
- Covalent bond
- Bond dipole moment
- Partial charge
- Molecular dipole