Identify the incorrect statement among the following:

• There is a decrease in the radii of the atoms or ions as one proceeds from La to Lu.

• Lanthanoid contraction is the accumulation of successive shrinkages

• As a result of lanthanoid contraction, the properties of 4d series of the transition elements have no similarities with the 5d series of elements

• Shielding power of 4f electrons is quite weak

C.

As a result of lanthanoid contraction, the properties of 4d series of the transition elements have no similarities with the 5d series of elements

The regular decrease in the radii of lanthanide ions from La³⁺ to Lu³⁺ is known as lanthanides contraction.
It is due to the greater effect of the increased nuclear charge than that of screening effect (shield) effect.
As a result of lanthanide contraction, the atomic radii of the element of 4d and 5d one close just above them in their respective group, so the properties of 4d and 5d transition element shows the similarities.