Question

Choose the incorrect statement among the following:

• A. the chemistry of different lanthanoids is very similar
• B. $4f-$ and $5f-$ orbitals are equally shielded
• C. $d-$block element show irregular and erratic chemical properties among themselves
• D. $La$ and $Lu$ have partially filled d-orbitals

Answer 1

The correct option is B $4f-$ and $5f-$ orbitals are equally shielded

Option A: True. The shielding of Lanthanoids is very similar.

Option B: False: $4f$ and $5f$ belong to different main energy levels, so the shielding effects on them are not the same. Shielding effect of 4f is more than that of $5f$.

Option C: True. $d-$ block elements are transition elements between metals and non-metals and hence, show irregular chemical properties among themselves.

Option D: Electronic configuration -

${}_{57}La:$ $\left[Xe\right]{6s}^2{5d}^1$

${}_{79}Lu:$ $\left[Xe\right]{6s}^2{4f}^{14}{5d}^1$

Both have partially filled d-orbitals.

Hence, B is the only option which is incorrect.