Identify the incorrect statement among the following:
- 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.
- There is a decrease in the radii of the atoms or ions as one proceeds from La to Lu.
Answer
(2) As a result of lanthanoid contraction, the properties of 4d series of the transition elements have no similarities with the 5d series of elements.
Solution
(1) Correct: the small shrinkages from one lanthanoid to the next add up — this cumulative effect is the lanthanoid contraction.
(3) Correct: 4f electrons shield each other poorly because of the diffused shape of f orbitals.
(4) Correct: radii of atoms/ions decrease steadily from La to Lu.
(2) Incorrect: as per NCERT, because of lanthanoid contraction the 4d and 5d series have almost identical radii (Zr 160 pm, Hf 159 pm), so their properties are very similar (Zr and Hf occur together and are hard to separate).
Answer: (2)