An element with electronic configuration $[Rn]\, 7s^2\, 5f^3\, 6d^1$ will fall in

Which of the following elements are analogous to the lanthanides?

What is the cause of lanthanoid contraction?

Identify all the correct statements for Lanthanide contraction.
$(A)$ The covalent properties of the Lanthanide metal hydroxides increase from $La$ to $Lu$.
$(B)$ The chemical reactivity decreases from $La$ to $Lu$.
$(C)$ $La(OH)_3$ is more basic than $Lu(OH)_3$.
$(D)$ $Zr$ and $Hf$ have about the same radius.
$(E)$ Separation of Lanthanides from one another is easy.

In lanthanides,with increase in atomic number,atomic radius decreases,except for the element $\underline{ X }$. What is $\underline{ X }$?

Describe the general chemical reactions of lanthanoids with the help of a diagram and state their uses.