Which of the following are considered as defects or anomalies in Mendeleev's periodic table? — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

The defects of Mendeleev's table include: uncertain position of Hydrogen (resembles both group I and VII), no separate places for isotopes (which have different atomic weights), placing unlike elements in the same group (e.g., Coinage metals with alkali metals), and anomalies in the atomic weight order (e.g., $Co$ and $Ni$, $Te$ and $I$).