# Any false chemical element in history of chemistry?

Was there any false chemical element introduced in history of chemistry? I mean a substance that after a while proved that it was not an element.

The example that comes to mind is didymium, which turned out to be a mixture of praesodymium and neodymium. The term is still used, as far as I know, to refer to glass doped with a mixture of these lanthanides. This is discussed in one of the 'Chemistry in its element' podcast episodes.

As it turns out, wikipedia has a category called 'Misidentified Chemical Elements'. Especially notable are illmenium, dianium and pelopium, which were all likely mixtures of niobium and tantalum, two rather similar elements.

One of the most important examples of a misidentified element is coronium. This element (or what was thought to be a new element) came to play a major role in our understanding of the Sun. Originally identified by spectroscopic analysis of the Sun's corona during a solar eclipse, coronium turned out to be iron so heavily ionized that to account for it, the corona must be heated to millions of degrees.

The question is: Was there any false chemical element introduced in history of chemistry?

The question is very broad, but the answers given so far are mainly based on modern time suggestions. For example, coronium was suggested as an element that 19th century scientists believed might exist in the corona of the sun, hence the name. According to Science Notes:

Coronium was suggested as a new element as the source of an unidentifiable green line in the spectra of the solar corona, which is visible during a total solar eclipse. This green emission line at $$\pu{530.3 nm}$$ was first observed by two scientists individually during the solar eclipse in August 7, 1869. This line did not correspond to the emission spectra of any known element at the time. Dmitri Mendeleev, known for developing the periodic table, proposed the name newtonium rather than coronium for this element who believed newtonium was an element slightly lighter than hydrogen.

It wasn’t until the 1930s that Walter Grotrian and Bengt Edlén determined the mysterious green spectral line observed during solar eclipses was due not to some unknown element, but to highly charged iron, $$\ce{Fe^{13+}}$$. Highly charged metal ions are responsible for other previously unidentified lines in the solar spectra, too.

However, I believe that the most important mis-identification of elements goes back to BCE time. Based on his previous philosophers ideas, Plato (428-347 BCE) has suggested that the terrestrial realm was imperfect, which was based on the four elements: (1) Earth; (2) Water; (3) Air; and (4) Fire. This theory was perfected by his best student, Aristotle adding some essence (Ref.1):

An element, we take it, is a body in which other bodies may be analyzed, present in them potentially or in actually (which of these, is still disputable), and not itself divisible into bodies different in form.

References:

1. Andrew Ede, The Chemical Element: A Historical Perspective; Greenwood Press: West Point, CT, 2006, pp. 13-15. ISBN 0-313-33304-1.