| Lanthanoids | Actinoids |
| Electronic configuration [Xe]4f1-14 50-1,6s2 | Electronic configuration [Rn] 5f1-14 6d0-1,7s2 |
| The differentiating electron enters the 4f subshell. | The differentiating electron enters the 5f subshell. |
| Except for Promethium all other elements occur in nature. | Except for Uranium and Thorium, all others are synthesized in the laboratory. |
| The binding energy of 4f electrons is higher. | 5f-orbitals have lower binding energy. |
| Only Promethium is radioactive. | All elements are radioactive. |
| Besides 3 + oxidation state they show 2 + and 4 + oxidation states. | Besides 3 + oxidation state they show 2 + , 4 + , 5 + , 6 + , 7 + oxidation states. |
| They have a less tendency to form complexes. | They have greater tendency to form complexes. |
| Many lanthanoid ons are colourless. Their colour is not as deep and sharp as actinoids. | Actinoids are coloured ions. Their colour is deep, e.g. U3+ is red and U4+ is green. |
| Lanthanoids cannot form oxo-cations. | Actinoids form oxo-cations such as – UO2+,PuO2+, UO22+, PuO22+ |
| Lanthanoid hydroxides are less basic. | Actinoid hydroxides are more basic. |
| Lanthanoid contraction is relatively less. | Actinoid contraction from element to element is comparatively more. |
| Mutual shielding of 4f electrons is more. | Mutual shielding effect of 5f electrons is less. |
