The difference between lanthanoids and actinoids are:Lanthanoids: They are involved in the filling of 4f- orbitals. The binding energy of 4f electrons is less than the 5f-electrons, which makes the lanthanoids less reactive. It is easy to achieve and describe the paramagnetic properties of lanthanoids. All lanthanoids are non-radioactive except promethium. They do not tend to form oxo-cations.Actinoids: They are involved in the filling of 5f-orbitals. The binding energy of 5f-electrons is higher, but the shielding effect is less effective than the 4f-electrons. All actinide elements are highly radioactive. Actinide forms oxo-cations, and their compounds are highly basic.