What are the elements of the $f$-block called?

Which of the following transition metal is present in misch metal?

$(i) La(OH)_3$ is the least basic among lanthanide hydroxides. $(ii) Zr^{4+}$ and $Hf^{4+}$ have almost identical ionic radii. $(iii) Ce^{4+}$ can act as an oxidizing agent. Which of the above statements are correct?

Which of the following is not a consequence of the Lanthanoid contraction?

The lanthanide for which $+II$ and $+III$ oxidation states are common is:

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