$Ce$ $(Z=58)$ is a member of

State the general electronic configuration of lanthanoids. Why are there irregularities in the electronic configuration of lanthanoids?

The most common oxidation state of Lanthanoid elements is $+3$. Which of the following is likely to deviate easily from $+3$ oxidation state?

The element californium belongs to the family of

Which of the following is not an actinide?

If the ionic radius of $_{57}La^{3+}$ is $1.06 \ \mathring{A}$,then the ionic radius of $_{71}Lu^{3+}$ will be approximately close to which of the following values in $\mathring{A}$?