Chemistry - f-block Question with Solution | TestHub

Question Explanation: We need to identify the incorrect statement based on lanthanoid contraction and alloy formation trends.

Concept: Alloys Formation

Lanthanoid contraction ⟶ 4d and 5d elements have nearly identical radii → affects density and ideal solid solution formation (Hume-Rothery rules).

Solution:

(1)$\mathrm{Zr}\approx$ Hf (almost same radii) → similar properties → difficult separation → correct

(2)$\mathrm{Nb}\approx \mathrm{Ta}$ radii → negligible lattice strain → ideal solid solution → correct

(3) 5d elements have similar volume but higher mass → density nearly doubles → correct

(4) $\mathrm{Ti}(132\mathrm{pm})$ is much smaller than $\mathrm{Zr}(160\mathrm{pm})$, while $\mathrm{Zr}\approx \mathrm{Hf}\to \mathrm{Ti}-\mathrm{Zr}$ is less ideal than $\mathrm{Zr}-\mathrm{Hf}\to$ incorrect