Consider the following statements 
1.The basic strength of hydroxides of lanthanides decreases from La$\left(\mathrm{OH}{)}_3\text{ to }\mathrm{Lu}\right(\mathrm{OH}{)}_3$
2.The lanthanoid ions ${\mathrm{Lu}}^{3+}{\mathrm{Yb}}^{2+}\text{ and }{\mathrm{Ce}}^{4+}$ are diamagnetic

3.the correct order of ionic radii of ${\mathrm{Ce}}^{3+},{\mathrm{La}}^{3+}{\mathrm{Pm}}^{3+}\text{ and }{\mathrm{Yb}}^{3+}\text{ is }{\mathrm{Yb}}^{3+}<{\mathrm{Pm}}^{3+}<{\mathrm{La}}^{3+}<{\mathrm{Ce}}^{3+}$ Which of the statements given above is/are correct?

$$\begin{gathered} \mathrm{Lu}=\left[\mathrm{Xe}\right]4{\mathrm{f}}^{14}5{\mathrm{d}}^{1}6{\mathrm{s}}^2;\mathrm{Yb}=\left[\mathrm{Xe}\right]4{\mathrm{f}}^{14}5{\mathrm{d}}^{0}6{\mathrm{s}}^2 \\ \mathrm{Ce}=\left[\mathrm{Xe}\right]4{\mathrm{f}}^{1}5{\mathrm{d}}^{1}6{\mathrm{s}}^2 \end{gathered}$$

Basic strength decreases from La(OH)₃​ to Lu(OH)_4​. 

Hence, (1) is incorrect. 

The given Ions contain no unpaired electrons and therefore, are diamagnetic. 

Hence, (2) is correct.

Atomic and ionic radii of Lanthanides decrease from La to Lu.

Their order of ionic radii:  ${\mathrm{Yb}}^{+3}<{\mathrm{Pm}}^{+3}<{\mathrm{Ce}}^{+3}<{\mathrm{La}}^{+3}$. Hence, (3) is incorrect.