Lanthanides

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

Europium is

Which one of the following statements concerning lanthanoid elements is false?

Lanthanum is grouped with $\mathrm{f}-$block elements because

Cerium $(\mathrm{Z}=58)$ is an important member of lanthanides. Which of the following statements about cerium is incorrect?

$\mathrm{Zr}$ and $\mathrm{Hf}$ have almost equal atomic and ionic radii because

Which is the correct order of their ionic size?

(Atomic numbers$: \mathrm{Ce}=58, \mathrm{Sn}=50, \mathrm{Yb}=70 \text{and} \mathrm{Lu}=71$)

Arrange ${\mathrm{Ce}}^{3+}, {\mathrm{La}}^{3+}, {\mathrm{Pm}}^{3+}$ and ${\mathrm{Yb}}^{3+}$ in the increasing order of their ionic radii.

Most common oxidation states of $\mathrm{Ce}$ (cerium) are

Which of following statements is not correct?

The lanthanide contraction relates to

Lanthanoids are

Rare-earth elements are exhibited by

Lanthanoid contraction occurs because

Lanthanoid for which $+\mathrm{II}$ and $+\mathrm{III}$ oxidation states are common is:

Among the lanthanides, the one obtained by synthetic method is:

General electronic configuration of lanthanoids is:

Identify the incorrect statement among the following:

Lanthanoids are:

In which of the following lanthanides, oxidation state $+2$ is the most stable?