Question

Similar sizes of second and third transition elements can be explained on the basis of −

• A. Inert-pair effect
• B. Screening effect
• C. Lanthanide contraction
• D. Increasing effective nuclear charge

Answer 1

The correct option is C Lanthanide contraction

In the third transition series after lanthanum, there is lanthanoid contraction. Due to this contraction, the size of any atom of the third transition series is almost the same as that of the element lying just above in the second transition series. This leads to the similarity in their radii.
Therefore, the correct answer is (C)