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?

Determine whether the following statements are True $(T)$ or False $(F)$:
$(a)$ All actinoid elements have a $7s^1$ configuration.
$(b)$ All actinoid elements have a $7s^0$ configuration.
$(c)$ There are no electrons in the $7s$ orbital of actinoids.

Which among the following properties of lanthanoids is $NOT$ true?

Which of the following statements is incorrect?

Describe the atomic and ionic radii of lanthanoids and explain lanthanoid contraction.

Which of the following elements can form compounds in $+3$ to $+7$ oxidation states?