Physical Properties of Lanthanides

The lanthanides are part of the periodic table, starting from the element lanthanum to lutetium. The atomic number of the elements starts from number 58 to 71. It is the first series in the periodic table that belongs to rare-earth metals. The magnetic properties of the lanthanides make them an important group of elements to be used in magnets across various industries. These are called the F-block elements and generally consist of a total of 15 elements. The lanthanides are considered rare earth metals due to the rare occurrence of the elements. This article sheds light on various physical properties of lanthanides like density, melting and boiling points and many more. 

Electronic Configuration and oxidation state of Lanthanides 

The common electronic configuration present in the lanthanoids is the 6s2. However, the occupancy of the 4f subshell in the lanthanide is variable depending on its atomic number. Hence, the value of n in the electronic configuration is from 1 to 14 in the increasing atomic number. The most common oxidation state in the lanthanide is +3, which means they can lose electrons to form a stable bond in a chemical reaction. Hence, the oxidation state of the lanthanoid varies from +2 to +4 depending on the element in the group.

Key features of Lanthanides 

• All the elements located in the lanthanide consist of only one valence electron in the 5d shell.

• Lanthanides are rare earth metals that belong to the 5d block of the periodic table. There are a few lanthanides that are formed during the fission of plutonium and uranium.

• The lanthanides have a silvery appearance with a lustre and shine.

• Moreover, the lanthanoids tend to become brittle when they are contaminated with various metals or non-metals.

• The lanthanides show a property called lanthanide contraction, which is the gradual decrease in the size of the element with an increase in the atomic number.

Physical Properties of Lanthanides

There are many physical properties specific to lanthanide, increasing their significance in various industry applications. Below are some properties of lanthanides:

• Magnetic properties 

Lanthanoid shows magnetic behaviour and hence is used for the production of magnets. The magnetic properties and paramagnetism of lanthanoids arise due to the presence of the unpaired electrons in the f-orbital.

1. The magnetic properties of lanthanide are represented by how it interacts with the magnetic field. It shows diamagnetic properties if it repels from the magnetic field. Also, it shows paramagnetic properties when it attracts the magnetic field.

2. The presence of the unpaired electrons leads to the magnetic properties in the lanthanoid. The total magnetic moment is calculated by totalling the orbital angular moment and the spin magnetic moment. 

• Melting and Boiling Points

The lanthanides have a very high melting point. The melting point ranges from 819 °C to 1663 °C but still makes it sensitive to contamination. It is found that irrespective of the high melting point, if it combines with oxygen or nitrogen, it becomes brittle. It has a very high boiling point which ranges from 1200 to 3500 °C. However, there is a particular or clear trend observed in the melting and boiling points starting from Lanthanum to Lutetium.

• Density 

The lanthanides are highly dense, with a density ranging from 6.1 to 9.8 grams per cubic centimetre. As the density increases, the atomic number also increases along with the periodic element in the lanthanoid. The density of the d-block elements (lanthanoids) is greater than the density of the s-block elements.

• Ionisation enthalpy

The ionisation enthalpy for the lanthanide is low, which is almost equal to the alkaline earth metals. The first ionisation enthalpies range from 500 – 600 kJ mol-1, whereas the second ionisation enthalpy for the lanthanide ranges from 1067 – 1200 Kj mol-1.

Formation of complex and other reactivity

• The lanthanides react with many elements to form a compound. For example, the lanthanoid reacts with carbon to form salt carbides, whereas it forms salty hydrides by reacting with hydrogen.

• Lanthanoids form oxides and sulphides on reacting with oxygen and sulphur, respectively.

• Lanthanides are ionic.

• The lanthanoids do not form many complexes due to the large size of tripositive lanthanide cations reducing electrostatic attraction and hence complex formation. 

• The high density of lanthanoids makes it a suitable element for the formation of alloys.

Use and applications of Lanthanides 

• The alloy of lanthanoids is used in metallurgical applications because it is mostly utilised as a reducing agent.

• Due to the magnetic properties of lanthanides, they are used in the production of magnets and electronic applications.

• They are used in ceramic applications. Ce(III) and Ce(IV) are used in the production of glass polishing powder. 

• The lanthanide elements are used in the development of nuclear control devices, fluxing devices, and shielding devices.

Conclusion 

The lanthanoid belongs to the d-group of the periodic table and rare earth metals. Some of the important physical properties include magnetic properties, high melting and boiling point, high density, and capacity to form complexes with other elements. The lanthanides are a series of elements that starts from lanthanum with an atomic number of 58 to lutetium with an atomic number of 71. The oxidation state of the lanthanoid ranges from +2 to +4. Due to its physical properties, it is used across various industries like ceramics, electronics, nuclear etc.