Practice question · Put in order
Order the key events in the historical development of the periodic table.
- Newlands proposes the Law of Octaves, periodicity every 8 elements (1865)
- Döbereiner groups elements into triads sharing similar properties (1817)
- Moseley shows atomic number (not mass) is the true basis of periodicity (1913)
- Mendeleev publishes table ordered by atomic mass; predicts missing elements (1869)
Hints
- Ordering by atomic mass came before ordering by atomic number.
- The correction that resolved the ordering anomalies came last.
Show the answer
- Döbereiner groups elements into triads sharing similar properties (1817)
- Newlands proposes the Law of Octaves, periodicity every 8 elements (1865)
- Mendeleev publishes table ordered by atomic mass; predicts missing elements (1869)
- Moseley shows atomic number (not mass) is the true basis of periodicity (1913)
Why
The modern periodic law (Moseley, 1913) replaced Mendeleev's mass-based ordering with atomic number ordering.
Practise Chemical periodicity
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