Same chapter3 marksDifficulty: Medium
State three achievements and two defects of Mendeleev's periodic table.
The Periodic Table
3 marksDifficulty: Medium
State two advantages of the modern periodic table over Mendeleev's table.
Original Khojo Papers practice question — not from a past board paper.
Answer
Isotopes, which have different atomic masses, occupy the same position because they have the same atomic number, so the difficulty they caused disappears. The anomalous pairs that Mendeleev had to place out of order of atomic mass fall naturally into place, and the position of hydrogen and the placing of the transition and rare earth elements are handled more satisfactorily.
No citable source has been recorded for this record. Treat it as practice material, not as fact.
Explanation
The modern table also makes the reason for periodicity clear: it follows from the filling of electron shells.
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