Talk:Q6643508

chemical element

@ArthurPSmith: There is a lot of discussions about chemicals element and there definitions. Can you explain in which spirit you removed the statement ? author  TomT0m / talk page 20:14, 14 January 2016 (UTC)

Inconsistent usage. Every other instance of chemical element (Q11344) is the element, not an "atom" of the element - it has a symbol, it has a periodic table group and period, phase properties, etc. Why would both hydrogen (Q556) and hydrogen atom (Q6643508) be instances of "chemical element"? Only one of those is regarding the element as an entry in the periodic table, with chemical properties, etc. An atom is in essence a primitive chemical compound - not even the diatomic molecule form of hydrogen which is how it normally manifests itself, in this case. It does have a wikipedia page (most individual atoms do not) so fine to have a wikidata item, but it's about the atom, which is distinct from the element. ArthurPSmith (talk) 20:21, 14 January 2016 (UTC)

@ArthurPSmith: are you aware the definition conflict of "chemical element" : in enwiki "pure chemical substance with a single type of atom (by atomic number)", in frwiki "type of atom (all atoms with some atomic numbers". Instances of the second definition are individual atoms, while instances of the first are individual substances. There is a lot of interwiki conflict induced. So there should be two "chemical element" items, that should be differentiated by the definition. author  TomT0m / talk page 12:19, 15 January 2016 (UTC)

@TomT0m: - thanks, no I wasn't aware of that difference. Are you sure the frwiki definition is correct, is it supported by strong references? Everywhere I look on the English web for a definition of "chemical element" it refers to a "substance" or "material", not a single atom. For example, Cambridge Dictionaries Online: "a ​substance that cannot be ​broken down into any ​simpler ​chemical ​substances and is made of ​atoms all of the same ​type". Also, looking at the application in practice, there are very few wikidata entries for "atoms" (hydrogen atom (Q6643508) and lithium atom (Q18201918) were the only two I could find) - so there really doesn't seem a need for a separate class. It seems unneeded complexity when we have entries for the element and the concept of an atom; what benefit is there from an additional derived item (except in cases as with this one where there is enough interest for its own wikipedia pages). ArthurPSmith (talk) 15:11, 15 January 2016 (UTC)

@ArthurPSmith: There is no complexity question at sake here, it's a POV question, and we should be able to reflect all POVs at sake. Having one item for every type of atom is nonetheless useful for a lot of points. Elemental substances WILL have statements like "has part : hydrogen atoms" anyway. The frwiki article quotes Antoine Lavoisier (Q39607)    for a definition as such. You'll also note that http://goldbook.iupac.org/C01022.html quotes "all atoms with the same number of protons in the atomic nucleus" as a définition after "species of atoms", which I read "type of atoms" in its definition 1. author  TomT0m / talk page 16:25, 16 January 2016 (UTC)

@TomT0m: Hmmm. So IUPAC sees two separate meanings for the term. But I would argue then that each "instance" of "chemical element" in wikidata also ought to reflect both meanings, not just one. So "hydrogen" refers to both the atom and substances containing just hydrogen atoms, while "hydrogen atom" is purely about the 1st IUPAC definition and therefore shouldn't be considered an "instance of" "chemical element". "hydrogen atom" should definitely be related to "hydrogen" in some way, perhaps via "part of" or perhaps a more customized property. ArthurPSmith (talk) 17:07, 16 January 2016 (UTC)

@ArthurPSmith: We need two items, this is the simplest and less confusing way to deal with different definitions. The "chemical element" def 2 definition of the UIPAC should just be simple substance (Q2512777), which is an official term used in french for this definition. Maybe we should have a third item such as "elementally simple atom or substance" which should be "disjoint union of" : "simple corps" ; "class of atom of a single atomic number" or something. author  TomT0m / talk page 17:54, 16 January 2016 (UTC)