Mendeleev's Periodic Table NEET Cheat Sheet: Everything You Need
Mendeleev's Periodic TableClassification of ElementsNEET ChemistryNEET 2025Periodic LawHistory of Periodic Table
Mendeleev's Periodic Table NEET Cheat Sheet: Everything You Need
Classification of Elements and Periodicity in Properties·2 min read·NEET 2026
What NEET Asks
Direct questions on Mendeleev's Periodic Law statement are common (1-2 marks).
Questions often test the basis of his classification or its limitations (e.g., anomalous pairs, isotopes).
Understanding predicted elements and their modern equivalents can fetch 4 marks.
Key Points
Mendeleev's Periodic Law (1869): "The properties of the elements are a periodic function of their atomic masses."
Elements were arranged in increasing order of atomic masses.
He also considered the similarities in chemical properties (especially formation of hydrides and oxides).
Merits: Left gaps for undiscovered elements (Eka-boron, Eka-aluminium, Eka-silicon), predicted their properties accurately, and accommodated noble gases without disturbing the existing table.
Demerits: Position of isotopes (same atomic number, different mass), anomalous pairs (e.g., Ar-K, Co-Ni, Te-I), position of hydrogen, and lack of clarity on cause of periodicity.
Eka-Aluminium corresponds to Gallium (Ga); Eka-Silicon to Germanium (Ge); Eka-Boron to Scandium (Sc).
Must-Know Concept
Mendeleev's Periodic Law: The physical and chemical properties of elements are periodic functions of their atomic masses.
Atomic Mass: The fundamental property used for arrangement.
Periodic Function: Properties repeat after regular intervals.
Common Mistakes
Students often confuse Mendeleev's basis (atomic mass) with the Modern Periodic Law's basis (atomic number).
Don't forget the specific anomalous pairs like Argon (Ar, mass 39.9) placed before Potassium (K, mass 39.1).
Students sometimes struggle to recall which modern elements correspond to Mendeleev's 'Eka' predictions.
Rapid Revision
Mendeleev classified elements by atomic mass and chemical properties, leaving gaps for predictions. Remember his Law, key merits like predicted elements (Eka-Al, Eka-Si), and crucial demerits, especially the anomalous pairs and isotope placement issues. This forms the foundation for the modern periodic table.
Frequently Asked Questions
What is Mendeleev's Periodic Law?▾
Mendeleev's Periodic Law states that the properties of elements are a periodic function of their atomic masses. This means that when elements are arranged by increasing atomic mass, their properties repeat after certain intervals.
What were the main advantages of Mendeleev's Periodic Table?▾
Mendeleev's table successfully predicted the existence and properties of several undiscovered elements, such as Gallium (Eka-aluminium) and Germanium (Eka-silicon). It also provided a systematic classification of known elements and allowed for the later inclusion of noble gases without significant disruption.
What were the major limitations of Mendeleev's Periodic Table?▾
Key limitations included the inability to place isotopes correctly (as they have different atomic masses but same chemical properties), the problematic placement of hydrogen, and the occurrence of anomalous pairs where elements with higher atomic masses were placed before those with lower atomic masses to maintain chemical similarity (e.g., Ar before K).
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