Mondo Knows Facts
Mendeleev left gaps for undiscovered elements
The 1869 table skipped spaces for elements that chemistry had not yet found Dmitri Mendeleev ordered the known elements by atomic weight and noticed that their properties repeated in a regular pattern. He left gaps where no known element fitted and predicted the density and chemistry of the missing ones. When germanium was isolated in 1886, it matched his forecast for eka-silicon closely. It sits in Mondo's science collection, one of 200 facts that each trace back to the reference below.
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Facts that can change over time are reviewed and updated. If something here looks wrong, Mondo would rather know than be confidently incorrect.
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Tags: periodic-table, chemistry, history
Mendeleev left gaps for undiscovered elements: the short answers
- Where does this come from, and can I check it?
- The 1869 table skipped spaces for elements that chemistry had not yet found. The figure is taken from Royal Society of Chemistry, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.
- Is this really a science fact?
- Yes. It sits on the Science shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.
- What else can I read about it?
- The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.