Lanthanides are the elements in the periodic table’s f-block of period six. These metals are transition metals, yet they have qualities that distinguish them from the rest of the elements. The actinide series, which spans the atomic numbers 89 to 103, is found in the periodic table’s sixth period and third group. The series is found beneath the main body of the periodic table, below the lanthanide series. Rare earth metals are divided into two groups: lanthanide and actinide. These substances are all radioactive and have a wide range of oxidation values. Uranium is the most prevalent and well-known element, and it is transformed into plutonium in a nuclear reaction to be utilised as nuclear fuel.

What are lanthanides?

Lanthanides have atomic numbers from 58 to 71. These are known as rare earth metals because the elements are found in the Earth’s crust in small quantities. A Norwegian mineralogist, Victor Goldschmidt, coined the name ‘lanthanide’ in 1925. The lanthanide family includes fifteen metallic elements, where except for one, all are f-block elements; these elements have 4f orbitals for their valence electrons.

Lanthanides are very dense metals having melting points that are greater than those of the d-block elements. With other metals, they create alloys. The inner transition metals, often known as the f block elements, are a subset of the f block elements. Electrons in the s, d, and f orbitals can be found in the inner transition elements/ions.

The general oxidation state of lanthanides and actinides

The first element in the group, lanthanum, has qualities in common with the others. Lanthanides are metals that are reactive and have a silvery tint. The lanthanides are commonly referred to as ‘rare earth’, yet they are not especially uncommon elements. Separating them, however, is challenging.

The valencies of lanthanides (Ln) and actinides (An) are both varied with elements having a primary oxidation state of +3. The additional valencies in the case of Ln are +2 and +4. There are several oxidation states in An, ranging from +2 to +7.

The oxidation state of lanthanides

The oxidation state of all lanthanide elements is +3. Some metals were formerly thought to have +2 oxidation states. A few lanthanide metals exhibit +4 oxidation states on rare occasions.

The oxidation state of lanthanides is affected by the stability of the f-subshell in such a way that the +4 oxidation state of cerium is preferred because it acquires a noble gas configuration, but it reverts to a +3 oxidation state and thus acts as a strong oxidant and can even oxidise water, though the reaction is slow.

Properties of lanthanide series

• They are the elements of the f orbital.
• They have a silvery, lustrous shine.
• They are soft metals that can be cut with a knife if necessary.
• Depending on the basicity of lanthanide, it is observed that the elements respond in different ways – where some respond quickly while others take longer.
• When contaminated with other metals or non-metals, lanthanides can corrode and become brittle.
• When exposed to air, silvery-white metals corrode and create oxides.
• The majority of them integrate to develop a trivalent compound. They can also produce divalent or tetravalent compounds under certain conditions.
• They have high boiling and melting points.
• They are soft metals and have a magnetic pull.
• They produce strong electromagnetic properties due to the presence of unpaired electrons.
• They have a strong magnetic field.

Consequences of lanthanide contraction

The effect of lanthanide contraction will be clearly depicted in the following points:

• Size of an atom
• The separation of lanthanides is difficult.
• Hydroxides’ fundamental strength is affected.

Physical properties of lanthanides

• Density: Because density is defined as the ratio of a substance’s mass to its volume, d-block elements have a higher density than s-block components. The density trend in the inner transition series will be the inverse of the atomic radii trend, i.e. density will rise as the atomic number grows over time.
• Melting and boiling points: Lanthanides have a very high melting point, although their melting and boiling points do not follow a distinct trend.
• Magnetic properties: Because of the unpaired electrons in orbitals, lanthanide atoms are called paramagnetic, except for f0 and f14, as they conduct a strong magnetic field. As a result, the diamagnetic states of Lu3+, Yb2+, and Ce4+ exist. Also, they have strong light and electromagnetic properties.
• ‘Orbital magnetic moment’ and ‘spin magnetic moment’ are both affected by unpaired electrons. The total magnetic moment is calculated by taking the orbital angular moment and the spin magnetic moment of the electrons into consideration.

Conclusion

All of the elements in the series are found in lanthanide minerals. The amount of each constituent, however, affects the price. Lanthanides are found in about equal amounts in the mineral euxenite.