Lanthanides and Actinides- The f-block elements

Lanthanides and Actinides

F block elements are divided into two series, particularly lanthanoids and actinoids. These blocks of elements are typically described as inner transition elements due to the fact that they provide a transition in the 6th and 7throw of the periodic table which separates the s block and the d block elements.

We see some hidden “layers” in the periodic table. As we look below the periodic table, we see two boxes– one between Ba (element 56) and Hf (element 72) and the other between Ra (88) and Rf (104). These elements all have unfilled f -subshells. Due to the uniqueness of the electronic configurations, these elements fit into the two boxes in the larger periodic table.

As the number of electrons in an atom increases, we begin to see some odd behaviours. Due to the way the electron energy levels work, some inner levels fill after several external levels do. We see this in two similar groups of elements– the lanthanides and the actinides.

F block elements are put separately at the bottom of the periodic table. They are a subset of 6th and 7th periods.


Classification of f- Block Components

The elements coming from the f block are additionally differentiated into:

  • The very first series of elements are called lanthanides and include elements with atomic numbers beginning from 57 and ending at 71. These elements are non-radioactive (except for promethium, which is radioactive).
  • The second series of elements are called actinides and include elements with atomic numbers beginning from 89 and ending at 103. These elements normally have a radioactive nature.

The row beginning with Lanthanum is the row including all the lanthanides whereas the row beginning with Actinium is the row that contains all the actinides.

Characteristic of Lanthanides
  • Lanthanides are soft metals of a silvery-white colour.
  • Their colour dulls and their brightness minimizes rapidly when exposed to air.
  • They have melting points varying from 1000K to 1200K (Except Samarium, 1623K).
  • Lanthanides are excellent conductors of heat and electricity as they have free electrons.
  • They are non-radioactive in nature except Promethium.
  • A decline in atomic and ionic radii from lanthanum to lutetium is seen. This is called the lanthanoid contraction.
Characteristic of Actinides
  • The Actinide elements seem silvery.
  • The Actinides have a radioactive nature.
  • These metals are extremely reactive and their reactivity increases when they are finely divided.
  • A reduction in atomic and ionic radii from Actinium to Lawrencium is seen. This is called the actinoid contraction.
  • They typically show an oxidation state of +3. However, elements belonging to the first half of the series are known to display greater oxidation states quite regularly.
Uses of Lanthanides

Lanthanides have been extensively utilized as alloys to impart strength and solidity to metals. The primary lanthanide utilized for this function is cerium, combined with percentages of lanthanum, neodymium, and praseodymium. These metals are likewise extensively utilized in the petroleum industry for refining of petroleum into gasoline items.

Erbium and other lanthanides are commonly used in some optical gadgets, such as night vision safety glasses, laser beams, and phosphorescent products.


Uses of Actinides

The actinides are valuable primarily since they are radioactive. These elements can be used as energy sources for applications as varied as cardiac pacemakers and generation of electrical energy for instruments on the moon. Uranium and plutonium have actually been utilized in nuclear weapons and in nuclear power plants.