The semantics of valence in chemistry is the ability of an atom to bond. In English, valence appears in several different quantitative connotations, besides composed terms like covalence, bond valence, and valence bond. For a numerical parameter, existence of alternative values due to differing perceptions is undesirable and obscures communication.
This project objective is to find out whether a comprehensive definition of valence can be formulated.
At the Inorganic Chemistry Division (Div II) meeting in 2016, it was decided to start a project to find out whether a comprehensive definition of valence can be formulated, with a task group that would include representatives of Divisions I (Physical and Biophysical), III (Organic and Biomolecular) and of the CCE (Chemistry Education).
Preparing the project, the task group chair conducted in 2016 a survey of numerical valence assignments among members of these IUPAC groups. It revealed that the valence use among chemists can be categorized into several, simple, heuristic, alternative definitions suitable for teaching.
The objective of this project is to test these possible definitions of valence on suitable examples and see whether one of them can be singled out behind the current use of the term while respecting the IUPAC reflectivity principle. That means deciding: A) Whether there is a definition of valence in a substantial current use that approximates the remaining alternative definitions by not grossly contradicting those of them that are unique or not derivative. B) Whether it yields numerical values that cover consistently the widest range of example compounds, while not contradicting other variables in current use that contain the term, e.g., bond valence.
If such a comprehensive definition of valence of an atom in a compound can be formulated and endorsed, heuristic algorithms will be worked out to evaluate its simple numerical value. If not, the analyses and examples will be included in the Technical Report that explains why no comprehensive definition of valence could be endorsed, concluding this Project. Valence will remain a term of different values, somewhat similar to electronegativity. In that analogy, suitable adjectives might discern such alternative valences.
The project of three parts will summarize at first the history and current usage of the term valence in chemistry and teaching, including relevant recent debates. This carries important etymology factor and will require a linguistic feeling. Alternative definitions of valence, implied by the surveys, will be validated against the current use in textbooks, papers and debates, and a list of possible definitions of valence will be set up.
In the second part, these alternative definitions of valence will be scrutinized against a series of practical examples. Each example in writing and drawing, subsequently by each member of the team, in an attempt to achieve a conclusion. After that, an insight should emerge whether or not a generalization is possible into the desired comprehensive definition of valence.
The third part are write-ups:
1. Technical Report or Provisional Recommendation.
If the latter:
2. Suggestion how to revise valence in the Gold Book.
3. Suggestion how to revise the Wikipedia entry.
4. Actual Wikipedia edit with associated discussions.
Page last update 22 Jan 2019