Some of the terminology that we use in chemistry can be extremely confusing for students! One such example is when we talk about bonding.
A bond is the name given when electrostatic forces of attraction between oppositely charged particles are balanced with the kinetic energy that would cause them to move away from each other in random directions. Put more simply:
“A bond is an electrostatic force of attraction between oppositely charged particles”.
Within chemistry, this is an extremely important idea. When approaching this topic, most literature will talk about intramolecular and intermolecular bonding. Confusingly, intramolecular bonding (meaning within molecules) will include ionic bonding alongside covalent bonding (including simple molecules and giant covalent structures). However, there are no molecules in giant ionic lattices. This is a breeding ground for misconceptions!
Intermolecular bonding (meaning between molecules) works much better as we only include temporary dipoles, such as London Dispersion Forces (LDF) and permanent dipoles, including hydrogen bonding. All the bonds encompassed here are between molecules, which makes perfect sense. Phew!
Beside the problem with ionic boning residing under the term intramolecular bonding, the whole system also completely ignores the electrostatic force of attraction between electrons and protons within an atom! This is incredibly important and students often cannot link this idea with the other concepts in bonding.
I therefore propose a new way of naming bonds that hopefully overcomes these challenges. This is summed up in figure 1. Unfortunately, you will need to zoom in at this point in order to see it fully, but hopefully, you can get the idea. The key features of this diagram are:
- It brings to the attention of the students that all of the bonding topic is about electrostatic forces of attraction between oppositely charged ions
- It accounts for the fact that bonding occurs within the atom between the electrons and the protons. This is termed intra-atomic bonding as it occurs within the structure of the atom. This has the potential to make students more aware of the fact that these can be broken in the same ways that normal bonds can be broken – by the increase in kinetic energy of the electrons.
- It renames intramolecular (meaning within molecules) to interatomic. This seems better suited to describing both ionic and covalent. Both ionic and covalent bonding involves the meeting of two or more atoms and then the distribution (whether uneven or even) of electrons between these atoms. Both involve the attraction of electrons in one atom with the protons in the nucleus of the other. Both are dependent on the electronegativity of the reacting atoms. Although the ionic bond is technically the electrostatic force of attraction between two oppositely charged ions, it is still brought about by the interconnection between two or more atoms.
- It makes it clear that hydrogen bonding is a subset of permanent dipole-dipole bonding. I think this is an important realisation for students. I think the terms for intermolecular bonding work quite well as they are.
How I would teach this is a matter for another blog post! In the meantime, I would love some feedback on this taxonomy.
Firstly, you will notice the glaring omission of metallic bonding. Where might this fit in?
Seconding, in more general terms: What do you think of this new naming? Is there anything I have missed? Are any of my definitions wrong? Am I completely off the mark? How might you use it in your teaching?