The separation of $Lanthanoid$ elements is based on which of the following?

Lanthanoid contraction is caused due to

What are the products formed when lanthanoids $(Ln)$ react with $1$. $H_2O$ and $2$. $N_2$?

Which one amongst the following are good oxidizing agents?
$A.$ $Sm^{2+}$
$B.$ $Ce^{2+}$
$C.$ $Ce^{4+}$
$D.$ $Tb^{4+}$
Choose the most appropriate answer from the options given below:

The most common lanthanide is

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 $4f^0$.