The first element of the rare-earth metals is:

Which oxidation state is common for lanthanoid elements?

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 $\mathring{A}$?

Identify the strongest base from the following.

Which of the following factors may be regarded as the main cause of lanthanide contraction?

Which element from the following has the smallest ionic size in the $+3$ oxidation state?