Applying Electronegativity: Polar vs. Covalent bonding
One of the most important applications of electronegativity is in understanding bonding.
- Take two atoms with very different electronegativities: fluorine (4.0) and cesium (1.0). Although we say that there’s a “bond” between fluorine and cesium, there isn’t much sharing of electrons going on. Instead, the attraction between these two is purely that of two point charges. We call this ionic bonding.
- Then take two atoms with the same electronegativity, say Cl–Cl. The atoms are of equal electronegativity, so this is a covalent bond. The pair of electrons between them is shared equally,
- Then there’s a lot of situations in between, where the electrons are shared *somewhat* equally, but not quite, because they have different electronegativities. These are called polar covalent – polar, because this unequal sharing leads to buildup of partial charges (that’s the delta, d) but not polar enough to be ionic. When we have two opposite charges adjacent to each other like this it’s called a dipole.
In this picture make sure you can see why the dipoles are this way.
In the near future, this is going to help explain boiling points and acidity.
In a few weeks, this is going help explain chemical reactivity.
Next tip: all about intermolecular forces.
Thanks for reading,