f-block Elements

The f-block elements, commonly known as the inner transition metals. They consist of two series: the lanthanides and the actinides. These elements exhibit similarities in their electronic configurations and chemical properties due to the filling of f-orbitals. If we talk about the position of f block elements in the Periodic table, f block elements in the Periodic table are placed separately at the bottom.

The lanthanide series comprises the 14 elements following lanthanum, ranging from cerium to lutetium. Actinides are the 14 elements succeeding actinium, starting with thorium and extending to lawrencium.

1.0What are f-block elements

The f-block elements, also known as inner transition metals, are found in the two series located at the bottom of the periodic table. These elements belong to the lanthanide and actinide series, distinguished by their placement within the f-orbital block.

2.0Classification of f block elements 

As we discussed above, f-block elements are classified into two series: the lanthanides and the actinides. The lanthanides belong to the sixth period and are located between groups 3 and 4, while the actinides belong to the seventh period and follow the lanthanides. These series consist of elements with partially filled f-orbitals.

Firstly let’s discuss the general differences between Lanthanides and Actinides in brief-

Electronic Configuration of Lanthanides and Actinides:

• The electronic configurations of the lanthanides and actinides are defined by the filling of their f-orbitals.
• For the lanthanide series (also known as the rare earth elements), the general outer electronic configuration can be expressed as [Xe] 4f^(1-14) 5d⁰ 6s². Each successive element adds one electron to the 4f sublevel, maintaining the 6s² and 5d⁰ configuration.

• Actinides follow a similar pattern, with the outer electronic configuration commonly expressed as [Rn] 5f^(1-14) 7s². As with the lanthanides, each successive element adds electrons to the 5f sublevel while retaining the 7s² configuration.

3.0Properties of f block elements 

The f-block elements, comprising the lanthanoids and actinoids, exhibit a range of unique properties that distinguish them from other elements in the periodic table.

In this section, we will discuss general properties of lanthanides and actinides.

Properties of Lanthanides

Lanthanides, also known as rare earth elements, exhibit several notable physical properties:

• 1. Metallic Nature: Lanthanides are silvery-white, malleable metals with high electrical conductivity.
• 2. High Density: They possess high densities; however, their densities vary across the series.
• 3. High Melting and Boiling Points: Lanthanides generally have high melting and boiling points, with some exceptions among the lighter lanthanides.
• 4. Magnetic Properties: Several lanthanides display unique magnetic properties, such as paramagnetism or ferromagnetism, especially at low temperatures.
• 5. Reduced Reactivity: Lanthanides are relatively reactive but tarnish slowly in air due to the formation of an oxide layer on their surface.
• 6. Variable Oxidation States: Lanthanides can exhibit different oxidation states, although the +3 oxidation state is the most common in compounds.

• 7. Similarity in Properties: The lanthanides share many chemical and physical characteristics due to their similar electronic configurations.

Properties of Actinides:

• 1. Radioactivity: Most actinides are radioactive, exhibiting different types of radioactive decay like alpha, beta, and gamma decay.
• 2. High Density: Actinides have high densities; for instance, uranium and plutonium are notably dense metals.
• 3. High Melting and Boiling Points: Actinides generally have high melting and boiling points, attributed to strong metallic bonding within their structures.
• 4. Variable Valency: These elements often exhibit various oxidation states due to the partially filled 5f orbitals, resulting in different valencies and chemical reactivities. The highest oxidation state is +7 (unstable) for Np and Pu, while the highest stable oxidation state is +6 for U.

• 5. Magnetic Properties: Some actinides display unique magnetic properties at low temperatures due to the interaction of their electronic orbitals.
• 6. Allotropy: Some actinides exist in multiple structural forms (allotropes) under different conditions, altering their physical properties.

4.0Similarities between Lanthanides and Actinides : 

Both lanthanides and actinides share several similarities:

Inner Transition Metals: 

• Both series are categorized as inner transition metals, occupying the f-block of the periodic table.

Similar Electronic Configurations:

• They have similar electronic configurations, with the electrons filling their f-orbitals. Lanthanides fill the 4f orbitals, while actinides fill the 5f orbitals.

Chemical Properties: 

• Both series exhibit similar chemical properties within their respective groups due to the filling of inner electron shells, resulting in comparable chemical behavior.

Radioactive Elements: 

• Many actinides are radioactive, and some of the heavier lanthanides exhibit slight radioactivity as well.

Applications: 

• Both lanthanides and actinides find applications in various industries, albeit for different reasons. Lanthanides are used in technologies like lighting, catalysts, magnets, and electronics, while actinides are employed in nuclear reactors, research, and sometimes in nuclear weaponry.

5.0Differences between Lanthanides and Actinides: 

Lanthanides and actinides are two series of elements classified as inner transition metals, but they have several differences:

Here's a summary table to highlight the differences between lanthanides and actinides: