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.