Question

The anomalous pairs in Mendeleev's periodic table is/are_______.

• A. Co, Ni
• B. Te, I
• C. Ar, K
• D. All the above

Answer 1

The correct option is D All the above

Anomalous pair is a set of two elements in which an element with higher atomic weight is placed before elements with lower atomic weight.

Example: $Co$ with atomic number 58.93 was placed before $Ni$ with atomic weight 58.61. Similarly, $Te$ (127.6 u) was placed before $I$ (126.9u), and $Ar$ (39.9u) was placed before $K$ (39.0).

Thus, all the given options form anomalous pairs.