Chemical Elements: How They Were Discovered (Repost)

About eighty years ago Clemens Winkler, the German chemist who discovered germanium which had been pre-dicted by D. Mendeleev under the name of "eka-silicon", likened the world of the elements to the theatre stage where scene after scene is played out with elements, as charac-ters. Each element, Winkler said, plays its own role. Sometimes it is a subsidiary role, sometimes it is a leading role.
In this way the scientist characterized the significance of the elements already discovered and known to man.
From the standpoint of the history of discovery, there can be neither leading nor subsidiary elements. All elements can lay equal claim to our attention.
Therefore, it is up to us to decide in what sequence the history of the discovery of the elements should be presented.
We can describe elements in the order of increasing atomic numbers: hydrogen, helium, lithium … up to element No. 107, which is still unnamed. Or we may describe the history of the discovery of the elements that compose the successive groups of the periodic system. Or we may deal with the elements in an alphabetical order.
We believe that all these ways of presentation are not very successful since they distort the chronology of discov-eries. And it is exactly the chronology that we want to make the basis of presentation here.
But at first let us try to understand clearly what is meant by the term "a chemical element".