Which of the following pairs of elements were placed in the inverted order of their atomic weights i — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

In Mendeleev's periodic table, the order of increasing atomic weights was not strictly followed in a few cases to group elements with similar properties together. These are called anomalous pairs. Examples include $Ar$ (39.9) before $K$ (39.1), $Co$ (58.9) before $Ni$ (58.6), and $Te$ (127.6) before $I$ (126.9).