Why is ionic bonding stronger than hydrogen bonding?
1 Answer
Ionic bonds are formed when two oppositely-charged ions come together. The interaction between these two ions is governed by the law of electrostatic attraction, or Coulomb's law.
According to Coulomb's law, these two opposite charges will attract each other with a force proportional to the magnitude of their respective charges and inverse proportional to the square distance between them.
Electrostatic attraction is a very strong force, which automatically implies that the bond formed between cations (positively-charged ions) and anions (negatively-charged ions) is considerably strong as well.
An important factor in determining the strenght of the electrostatic attraction between the two ions is the magnitude of their charges. Here is where ionic bonds greatly differ from hydrogen bonding, which represents an intermolecular bond.
Hydrogen bonding takes place between hydrogen and one of the three most electronegative elements in the periodic table, N, O, and F. When bonded with hydrogen, these three elements determine the formation of partial charges in the molecule.
Because of their high electronegativities, these elements will hog more of the electron density, becoming partial negative; at the same time, hydrogen will become partial positive, since the electron cloud will now spend more time around the more electronegative atom.
The partial positive ends of the molecule will now be attracted by the partial negative ends of another molecule, and so on; however, the magnitude of these partial charges is considerably weaker than the magnitude of the charges created when electrons are lost/gained, like they are for cations and anions.
The result is of course that hydrogen bonds are nowhere near the strenght of an ionic bond, which is considered to be the strongest type of bond altogether.
