ScienceEurope
The periodic table
Mendeleev left blank spaces — and was proved right
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That a system can predict something not yet observed is the very mark of a good scientific theory. The pattern was explained only by quantum mechanics fifty years later: the periods correspond to electron shells. The table is probably the most recognisable diagram in all of science.
For children
Mendeleev arranged the elements by weight and properties and found they fall into a pattern. Where the pattern had gaps, he predicted unknown elements — and described their properties. When they were found, he was right.
Connects to
Part of Terra Saga — the story of Earth on a timeline. terrasaga.org