For the general electronic configuration $(n-2)f^{1-14}(n-1)d^{0-1}ns^2$,if $n=7$,the configuration belongs to which series?

What is the effect of lanthanoid contraction in the lanthanoid series of elements?

Fill in the blanks:
$1.$ The atomic radii of the elements of the third transition series are .......... to those of the corresponding elements of the second transition series.
$2.$ Samarium melts at .......... $K$.
$3.$ The color of lanthanoid ions is due to the presence of .......... electrons.

Which of the following lanthanoid ions is diamagnetic?
(At. nos. $Ce = 58, Sm = 62, Eu = 63, Yb = 70$)

$A$ member of the Lanthanoid series which is well known to exhibit $+4$ oxidation state is

Which statement is incorrect among the following?