ABSTRACT
In several scientific disciplines, chemical elements are conventionally separated as major elements and 'traces' based on thresholds of concentration. The word 'traces' evokes analytical difficulty in determining low concentrations, with no relationship to any property or function. Trace elements can therefore be metals (e.g.: Cd, Cs, Cu, Ni, Pb, Z n ,...) or non-metals (e.g.: F, Cl, B, I , ...). Metals are defined according to their physical properties (high electrical and thermal conductivity, high reflectivity, malleability), which are largely explained by their chemical properties (essentially the tendency to donate electrons).
