Chemistry - f-block Question with Solution | TestHub

${\mathrm{Y}}^{3\oplus }$

$\wedge$

${\mathrm{La}}^{3\oplus }>{\mathrm{E}}_4^{3\oplus }>{\mathrm{L}}_4^{3\oplus }$

Ionic radii of ${\mathrm{Y}}^{3\oplus }$ is smallest among given 4 ions because

Ionic radius $\propto$ no. of shell

${\mathrm{Y}}^{3\oplus }<{\mathrm{Lu}}^{3\oplus },{\mathrm{Eu}}^{3\oplus }$ and ${\mathrm{La}}^{3\oplus }$

${\mathrm{Lu}}^{3\oplus },{\mathrm{E}}_4^{3\oplus }$ and ${\mathrm{La}}^{3\oplus }$ are isoelectronic so ionic radii order will be :

Ionic radius $\propto \frac{1}{Z_{eff}}$

${\mathrm{Lu}}^{3\oplus }<{\mathrm{Eu}}^{3\oplus }$$\underset{<{\mathrm{La}}^{3\oplus }}{}$

So, the final order of ionic radius will be :

${\mathrm{Y}}^{3\oplus }<{\mathrm{Lu}}^{3\oplus }<{\mathrm{Eu}}^{3\oplus }<{\mathrm{La}}^{3\oplus }$