Q. The hardest lanthanide element is
Solution:
Hardest lanthanide element is lutetium $\left({ }_{71} Lu \right)$. But among the given options gadolinium (Gd) is the hardest lanthanoid.
Hardness of few lanthanide elements on vicker's scale is given below.
Lanthanides
Hardness (M Pa)
$57^{ L a}$
491
${ }_{62} Sm$
412
${ }_{64} Gd$
570
${ }_{66} Dy$
540
${ }_{70} Yd$
206
| Lanthanides | Hardness (M Pa) |
|---|---|
| $57^{ L a}$ | 491 |
| ${ }_{62} Sm$ | 412 |
| ${ }_{64} Gd$ | 570 |
| ${ }_{66} Dy$ | 540 |
| ${ }_{70} Yd$ | 206 |