The concept chemical bonding is exceptional. It is a fundamental concept in understanding what chemistry is about; it is discussed several times and at various levels during the advanced course, but still, very few students (15.7%) provided an explanation expressing a profound understanding of it. Most students in the advanced course (both 11th and 12th grade) provided examples of chemical bonds, but did not explain the essence of the concept. Typical answers were, “It is a bond inside molecules and between molecules”; “Ionic, metallic, covalent, van der Waals, and hydrogen bonds are chemical bonds”. This kind of answer was classified as ‘partially correct’ but not as ‘correct and accurate’ since the answers do not provide any explanation of the essence of the concept. This does not necessarily mean that students who provided this kind of explanation really do not know what a chemical bond is. It is more likely that they were never asked to explain the meaning of it. The usual practice in the advanced course is to focus on the differences between bonds (for example, Van der Waals bonds are weaker than hydrogen bonds) rather than explain the common basis of all chemical bonds. Understanding that a chemical bond is based on the electrical attraction between particles is considered to be more important for chemical literacy, rather than citing the names of bonds (Levy-Nahum et al., 2004). Thus, we think it advisable to emphasize the general nature of chemical bonds, before teaching about the many types of chemical bonding as disconnected pieces of knowledge.