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Lanthanides and Actinides

Lanthanides and actinides are two prominent families of the periodic table of elements. Discussed below are the differences between the elements in these two families and their common properties.

Why are the Lanthanide and Actinide Series Separated from the Periodic Table

Lanthanide and actinide are separated from the main body of the periodic table because of how electrons get filled up. They belong to the category of f-bock elements in which the f subshell is progressively filled as electrons are added to the atoms. The properties of these elements differ from d-block and s-block. Another reason for placing them below the main body is that they fill up too much space and for the simplicity of printing on a standard letter size paper.

Lanthanides and Actinides on the Periodic Table

Differences and Similarities between Lanthanides and Actinides

What are the Differences

Lanthanides Actinides
Rare-earth elements Not rare-earth elements
Reasonably abundant on the surface of the earth Synthesized in the laboratory (except uranium, thorium)
4f shell filled progressively 5f shell filled progressively.
Non-radioactive (except promethium) Radioactive
Do not form oxocations Form oxocations
Form compounds that are low in basicity Form compounds that are high in basicity
Have a low tendency to form complexes with ligands Have a high tendency to form complexes with ligands
Colorless Most ions are colored
Display maximum oxidation state of +4 Display maximum oxidation states of +6

What Do They Have in Common

Belong to the family of inner transitional metals
Have their f shell filled progressively by electrons
Have a common oxidation state of +3
Show contraction in their atomic radii
Highly electropositive and highly reactive

Why Actinides Have Greater Tendency to Form Complexes than Lanthanides

Actinides have a greater tendency to form complexes than lanthanides because their ions are smaller and have a large concentration of charges. Therefore, actinides have high nuclear density than lanthanides. Besides, the 4f orbitals in the Ln3+ ion do not participate directly in bonding since the 5s2 and 5p6 orbitals shield it entirely.