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Module 5-Mendeleev's Periodic Table Genius

Sep 10, 2025

Overview

This lecture discusses Dmitri Mendeleev's creation of the periodic table, highlighting his predictive genius and the impact of his scientific achievements.

The Periodic Table and Its Origins

  • The periodic table is a widely recognized scientific tool organized by Dmitri Mendeleev.
  • Mendeleev was not the first to list or group elements by properties.
  • Earlier attempts at arranging elements did not achieve the predictive power of Mendeleev's table.

Mendeleev's Scientific Insight

  • Mendeleev's genius lay in leaving intentional gaps for undiscovered elements.
  • He used the properties of surrounding elements to predict the properties of missing ones.
  • For the gap later known as "eka-aluminum," he predicted atomic weight, physical state, appearance, conductivity, malleability, melting point, and density.

Verification of Predictions

  • Gallium, discovered by Paul Emile Lecoq de Boisbaudran, matched Mendeleev's predictions for eka-aluminum.
  • Gallium's atomic weight (69.72) and density (5.9 g/cm³) closely matched Mendeleev's estimates.
  • Other elements predicted included scandium, germanium, rhenium, and technetium (formerly eka-manganese).

Mendeleev's Legacy

  • Mendeleev died in 1907 without a Nobel Prize.
  • In 1955, element 101 was discovered and named Mendelevium in his honor.
  • Only 15 scientists have elements named after them, highlighting the rarity of this recognition.

Key Terms & Definitions

  • Periodic Table — An organized chart of chemical elements arranged by atomic number and similar properties.
  • Atomic Weight — The average mass of atoms of an element, measured relative to hydrogen.
  • Eka-aluminum — Mendeleev’s predicted element one place beyond aluminum, later discovered as gallium.
  • Technetium — Rare element predicted as eka-manganese, first synthesized in 1937.

Action Items / Next Steps

  • Review properties and trends of the periodic table’s groups and periods.
  • Read more about the discovery and confirmation of predicted elements.