With reference to structural variability and chemical reactivity, write the differences between lanthanoids and actinoids.

Explanation

Structure : All the lanthanoids are silvery white soft metals. Hardness of Lanthanoids increases with increasing atomic nuinber.
The actinoid metals are all silvery in appearance but display a variety of structures. The structural variability is due to irregularities in metallic radii which are greater than that of lanthanoids.
Chemical reactivity : Earlier members of lanthanoid series are quite reactive similar to calcium but with increasing atomic number they behave more like aluminium.
The actinoids are highly reactive in finely divided state.