Ferrous oxide is more basic in nature than the ferric oxide

Ferrous compounds are relatively more ionic than the corresponding ferric compounds

Ferrous compounds are less volatile than the corresponding ferric compounds

Ferrous compounds are more easily hydrolysed than the corresponding ferric compounds.

All the members exhibit +3 oxidation state

Because of similar properties the separation of lanthanoids is not easy.

Availability of 4f electrons results in the formation of compounds in +4 state for all the members of the series.

There is a gradual decrease in the radii of the members with increasing atomic number in the series.

$$4{f^3}\,5{d^5}\,6{s^2}$$

$$4{f^8}\,5{d^0}\,6{s^2}$$

$$4{f^4}\,5{d^4}\,6{s^2}$$

$$4{f^7}\,5{d^1}\,6{s^2}$$

In addition to the normal oxidation states, the zero oxidation state is also shown by these elements in complexes.

In the highest oxidation states, the transition metal show basic character and form cationic complexes.

In the highest oxidation states of the first five transition elements (Sc to Mn), all the 4s and 3d electrons are used for bonding

Once the d⁵ configuration is exceeded, the tendency to involve all the 3d electrons in bonding decreases.