Question

The hardest lanthanide element is

• A. $Sm$
• B. $La$
• C. $Gd$
• D. $Dy$
• E. $Yb$

Answer 1

Answer: (C)

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)
$57^{La}$	491
${}_{62}Sm$	412
${}_{64}Gd$	570
${}_{66}Dy$	540
${}_{70}Yd$	206