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Mendeleev's Periodic Table Overview

May 19, 2025

Mendeleev's Periodic Table - AQA - GCSE Chemistry Revision

Overview

  • Dmitri Mendeleev: Russian chemist who developed an early periodic table in 1869.
  • Arranged elements by increasing atomic weights and properties.
  • Modern periodic table arranges elements by atomic number.

Early Classification Attempts

  • Elements were initially arranged by atomic weight.
  • Resulted in incomplete tables and some misclassified elements.

Mendeleev's Periodic Table

  • Gaps: Left for undiscovered elements, allowing predictions of their properties.
  • Predictions: Successfully predicted properties of elements like 'eka-silicon,' which turned out to be germanium.

Specific Adjustments

  • Pair Reversals: Example with iodine and tellurium.
    • Iodine should have come before tellurium (based on atomic weight) but was placed after due to similar chemical properties with chlorine and bromine.

Key Concepts

  • Atomic Weight vs. Atomic Number:
    • Mendeleev used atomic weight; modern tables use atomic number.
  • Properties:
    • Chemical properties influenced Mendeleev's arrangement.

Modern Context

  • Mendeleev's table laid the foundation for modern periodic tables.
  • Predicted elements validated his organizational strategy.

Additional Resources

  • Explore more with BBC Bitesize on topics like Atomic Structure, Properties of Metals and Non-Metals, and Transition Metals.