Question

Anomalous pair in Mendeleev's periodic table is:

• A. $Li,Na$
• B. $Mg,Al$
• C. $Co,Ni$
• D. $Be,B$

Answer 1

The correct option is C $Co,Ni$

Some elements with higher atomic weight were placed before low atomic weight elements in order to maintain the similar chemical nature of elements and are called inverted pairs or anomalous pairs.

Anomalous pairs of Mendeleev's periodic table are $Ar-K,Co-Ni,Te-I,Th-Pa$.