[cliverlong]

Hi,

  Does anyone have a definition of a chemical element that does not make reference to atoms?



Clive

[azmanam]

Most strictly, an element is defined by the number of protons it has. 

You can increase or decrease the neutrons (isotopes).  You can increase or decrease the electrons (ions).  But the element is still the same.  But increase or decrease the number of protons, and you change the element.

[cliverlong]

Most strictly, an element is defined by the number of protons it has. 

You can increase or decrease the neutrons (isotopes).  You can increase or decrease the electrons (ions).  But the element is still the same.  But increase or decrease the number of protons, and you change the element.

Yes, very good.

But implicit in my question was to find a definition of element contains no reference to atoms or any particle that might comprise or constitute the sub-structure of an atom.

Think of how a chemist in the mid-19th Century, pre- a "commonly agreed" (*) atomic theory would define an element. How would such a chemist classify the following  he / she might be familiar with as elements or compounds? (using modern names)

Copper
Tin
Water
Mercury (II) Oxide
Lead (II) Sulphide


Thanks

Clive

(*) I'm assuming that at that time there were various contradictory ideas of what atoms were and also arguments that atoms didn't exist.
(*) I'm also assuming that the concept of element was widely used in chemistry even if the concept of atom (or its constituent parts) was poorly understood at that time

[azmanam]

I read a book a while back, A Chemical History Tour (http://www.amazon.com/Chemical-History-Tour-Picturing-Chemistry/dp/0471354082/).  I forget most of the details, but it was fascinating and talked about many of the concepts you're wondering about.  If you're at a major university, the library probably has it (mine did).

[enahs]

Aristotle said:
"Element – one of those bodies into which other bodies can be decomposed and which itself is not capable of being divided into other."

The more modern definition of an element, but before atomic theory comes from Robert Boyle. It states the same thing as Airstotle, but Airstotle and those before Boyle were more into philosophical arguments about what elements are; such as fire, air, water and earth.

[cliverlong]

azmanam

Thanks for the link. It has lead me to a few "candidate" books that should cover this topic.

enahs

Thanks for reminding me that although the term element has been around for a long time it meant something quite different to the modern idea for most of that time. I will look into various links and the books from azmanam's suggestion to understand what Boyle proposed.

Thanks

Clive