Question

the members of actinods series exhibit a large number of oxidation states than the corresponding member of lanthanoid series

Answer 1

Chemistry of the lanthanides differs from actinides because of the nature of the 4f orbitals. These orbitals are buried inside the atom and are shielded from the atom's 4d and 5p electrons. As a result, the chemistry of the elements is largely determined by their size, which decreases gradually with increasing atomic number. This phenomenon is known as the lanthanide contraction. Therefore All the lanthanide elements exhibit the oxidation state +3.