About of mendlif periodic table in chemistry

 

Mendeleev's Periodic Table (1869)

Dmitri Ivanovich Mendeleev, a Russian chemist, created the first successful periodic table of elements in 1869. He arranged elements based on their atomic mass and similar chemical properties.

Key Features of Mendeleev's Periodic Table

  1. 🔢 Arrangement by Atomic Mass:

    • Elements were arranged in increasing order of atomic masses.
    • E.g., Lithium (7), Beryllium (9), Boron (11), etc.

  2. 🧪 Groups and Periods:

    • Vertical columns were called Groups (with similar chemical properties).
    • Horizontal rows were called Periods.

  3. ❓ Gaps for Undiscovered Elements:

    • Mendeleev left blank spaces for elements not yet discovered.
    • Predicted properties of unknown elements like eka-aluminium (Gallium), eka-silicon (Germanium), etc.

  4. 🔄 Correction of Atomic Masses:

    • He corrected the atomic masses of some elements (like Beryllium and Indium) to fit them properly.

  5. ⚠️ Anomalies:

    • Some elements with higher atomic mass were placed before those with lower atomic mass to maintain chemical similarity.
    • Example: Cobalt (58.9) placed before Nickel (58.7).

Merits of Mendeleev’s Table

  • Helped discover new elements.
  • Predicted properties of unknown elements.
  • Grouped similar elements together.

Limitations of Mendeleev’s Table

  1. Position of Hydrogen was unclear.
  2. Isotopes couldn’t be explained (same element, different mass).
  3. Irregular placement of some elements due to mass anomalies.

Modern Relevance

  • Mendeleev's table formed the foundation of the Modern Periodic Table, which is based on atomic number (not atomic mass), developed by Henry Moseley in 1913.

Let me know if you want this explained in Hindi or with a diagram!

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