The lanthanide contraction is responsible for the fact that - Vidyadip

MCQ

The lanthanide contraction is responsible for the fact that

A
$Zr$ and $Y$ have about the same radius
B
$Zr$ and $Nb$ have similar oxidation state
✓
$Zr$ and $Hf$ have about the same radius
D
$Zr$ and $Zn$ have the same oxidation sate

✓

Answer

Correct option: C.

$Zr$ and $Hf$ have about the same radius

c
Due to lanthanide contration the size for $Zr$ and $Hf$ is same. Lanthanide contraction can be explained on the basis of shielding effect.In multi-electron atoms the electrons are added in outer shells. The electrons already present in inner shells, shield the outer electrons from nuclear charge, making them experience a lower effective charge of the nucleus. The shielding effect exerted by the inner electrons decreases in the order $s > p > d > f$. This $f$ subshell poorly shields the outer electron from nuclear attraction which results in more attractive pull of nucleus on outer electron and smaller size.In case of post lanthenide elements like $Hf , 4 f$ subshell is filled and it is not very effective at shielding the outer shell $(n=5$ and $n=6)$ electrons. it is similar to $Zr$.

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