Is chemistry really that simple? If we focus on the concept of molecules and their chemical bonds, indeed we can obtain all their numerical properties by solving the appropriate equations; we (ideally) get the energies and other values due to Hermitian operators (like the Hamiltonian), and at the same price we may obtain the wave function. But this will not respond to conceptual notions, such as what on earth is a chemical bond. Or, as Coulson defiantly said: "I described a bond, a normal simple chemical bond; and I gave many details of its character. Sometimes it seems to me that a bond between two atoms has become so real, so tangible, so friendly that I can almost see it. And then I awake with a little shock: for a chemical bond is not a real thing, it does not exist, no-one has ever seen it, no-one ever can. It is a figment of our own imagination." Except for specific cases, in general we are missing an important side of chemical education by not teaching and debating history and philosophy of chemistry. In particular, and regarding the present article, it is our belief that one important aspect that is lacking in chemistry education is the recognition of how much we do not know about the chemical bond. There is a large and solid body of literature about teaching this topic, with most of these sources emphasizing the best strategies to teach the bond and to test the students on the topic, as well as bringing tools to minimize the students' lacunas in knowledge, comprehension, and metacognition from high-schoolers to advanced undergraduates. However, to the best of our knowledge, these works do not incorporate the teaching of the scientific uncertainties of the bond, that is the "known unknowns" for researchers, but "unknown unknowns" for students.