When Lanthanoids $(Ln)$ react with oxygen $(O_2)$,what is the product $X$?

Which of the following elements belongs to the inner transition elements?

Determine the correct $(T)$ and incorrect $(F)$ statements from the following:
$(a)$ The symbol for Lanthanum is $La$.
$(b)$ The name of the element $Lu$ is Lanthanum.
$(c)$ The electronic configuration of $La^{3+}$ and $Ce^{4+}$ contains $4f^0$.

Fill in the blanks given below:
$(i)$ Neptunium and Plutonium are obtained from ............ .
$(ii)$ Lanthanoid series and Actinoid series are known as ............ .
$(iii)$ The main energy level of an atom is called ............ .
$(iv)$ Elements that possess both metallic and non-metallic properties are called ............ .

The main reason for the actinoids exhibiting a larger number of oxidation states than the lanthanoids is:

Arrange the ions $Ce^{3+}$,$La^{3+}$,$Pm^{3+}$,and $Yb^{3+}$ in the increasing order of their ionic radii.