Which of the following compounds is the most acidic?

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

The outer electronic structure of lawrencium (atomic number $103$) is

On the basis of Lanthanoid contraction,explain the following :
$(i)$ Nature of bonding in $La_2O_3$ and $Lu_2O_3$.
$(ii)$ Trends in the stability of oxo salts of lanthanoids from $La$ to $Lu$.
$(iii)$ Stability of the complexes of lanthanoids.
$(iv)$ Radii of $4d$ and $5d$-block elements.
$(v)$ Trends in acidic character of lanthanoid oxides.

Identify the ion having $4f^6$ electronic configuration.

Assertion : Magnetic moment of $Dy^{3+}$ is highest among lanthanoids.
Reason : Orbital motion contributes to the magnetic moment.