Chemical elements known as actinides are found in the F-block of the periodic table. The F-block of their atoms contains their valence electrons. As they are present in the form of metals, they are known as inner transition metals. 

The F-block only consists of lanthanides and actinides. A chemical named actinium is why the series is known as actinide, and a chemical called lanthanum, the reason for the name being lanthanide. The most crucial difference between lanthanide and actinides is that actinides form complexes more easily than lanthanides.

Lanthanide

Lanthanides are the elements whose last electron enters the 4F orbitals. Due to only one oxidation state, lanthanides resemble each other more than any other transition elements in the series. Their chemical properties and similar elements are why they got the excellent opportunity to obscure the effect of small changes in size and the nuclear charge. Their three shells are incomplete in their general configuration. Their common oxidation state is +2, and all elements contain that in the series. 

Some exceptions of lanthanide series include +4 oxidation state naming cerium, praeseodymium and terbium. Pr, Nd, Dy and Tb exhibit +4 oxidation states, but only in oxides. In tri-positive ions, in its 4f subshell, the number of unpaired electrons increases from lanthanum to gadolinium. So lanthanum and lutetium are diamagnetic, and others are paramagnetic. Lanthanides have a high melting point. 

Electropositive character is high due to low ionisation power. Due to the large size, they have a low charge and thus do not have much tendency to form complexes.

• lanthanum La (57)

• cerium Ce (58)

• Praseodymium Pr (59)

• neodymium Nd (60)

• promethium Pm (61)

• samarium Sm (62)

• Europium Eu (63)

• Gadolinium Gd (64)

• Terbium Tb (65)

• dysprosium Dy (66)

• Holmium Ho (67)

• yttrium Er (68)

• thulium Tm (69)

• ytterbium Yb (70)

• Lutetium Lu (71).

Actinides

Actinides are elements whose last electron enters the 5f orbital of the anti-penultimate shell. In contrast to lanthanoids, Actinides are far more complicated, owing to several oxidation states and their radioactivity. In actinides, +3 is the most common oxidation state.

As the atomic number increases in the actinide series, the more stable the oxidation state becomes. A small energy gap between 5f, 6d and 7s subshells are present, so they show a more significant number of oxidation states than lanthanides. They exist in a silvery colour and can display multiple structures. The metals are quite reactive when divided finely. Their magnetic properties are far more complex than lanthanides.

• thorium Th (Z=90)

• protactinium Pa (91)

• uranium U (92)

• neptunium Np (93)

• plutonium Pu (94)

• Americium Am (95)

• curium Cm (96)

• berkelium Bk (97)

• californium Cf (98)

• einsteinium Es (99)

• fermium Fm (100)

• mendelevium Md (101)

• a unit Ї 102

• lawrencium Lr (103).

Lanthanide vs actinide

Conclusion

The chemical elements actinides and lanthanides are present in the f block of the periodic table. Radioactive elements are present as actinides. With a few exceptions, lanthanides are non-radioactive elements. The primary distinction between actinides and lanthanides is that actinides may quickly form complexes, whereas lanthanides cannot. Actinides are more radioactive, and lanthanides are not.

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