Actinoids: Electronic Configuration and the Oxidation States

Actinoids are elements with atomic numbers ranging from 90 to 103, which come after the element Actinium. They include naturally occurring thorium, protactinium, and uranium elements, as well as eleven transuranic elements created artificially through nuclear processes. Despite this, all Actinoids are radioactive.The term “actinide series” comes from the first element in the series, actinium. The symbol An is used to refer to any of the actinide series elements, which have atomic numbers ranging from 89 to 103 on the periodic table.

All elements in the actinide series are radioactive in nature, releasing a considerable amount of energy during radioactive decay. The most numerous naturally occurring Actinides on Earth are uranium and thorium, while plutonium is synthesized.

These elements are present in nuclear reactors as well as nuclear weapons. americium is used in the ionization chambers of modern smoke detectors.

lanthanoids and actinoids are seen as 2 distinct rows below the main periodic table in the modern periodic table.

Actinoids have the following general electronic configuration:  Radium is the nearest noble gas, and its electronic configuration is [Rn] 7s²

Actinide Electronic Configuration

Actinides are the second series of f-block elements, with a terminal electronic configuration of [Rn] 5f^1-14 6d^0-17 s² ,because the energies of 5f and 6d electrons are close, electrons enter the 5f orbital.

Actinoids Contraction

Due to increasing nuclear charge and electrons entering the inner (n-2) f orbital, the atomic size/ionic radius of tri positive Actinoids ions decreases steadily from Th to Lw. Actinide contraction, like lanthanide contraction, refers to the gradual decrease in size with increasing atomic number. Contraction is greater along the period due to the very poor shielding by 5f electrons.

Coloured Ion Formation

Actinoids, like lanthanides, have electrons in f-orbitals as well as empty orbitals, as do d-block elements. The f-f electron transition produces visible color when a frequency of light is absorbed.

Actinide Ionization

Because 5f electrons are more effectively shielded from nuclear charge than 4f electrons, Actinoids have lower ionization enthalpies than lanthanides.

Actinide Oxidation State

Because of the smaller energy gap between the 5f, 6d, and 7s orbitals, Actinoids have variable oxidation states. Though 3+ is the most stable oxidation state, due to the good shielding of f-electrons, other oxidation states are possible. The maximum oxidation state tends to increase up to the mid of the series and then decreases; for example, it increases from +4 for Th to +5, +6, and +7 for Pa, V, and Np but decreases in the succeeding elements.

Formation of Complexes

Because of their smaller size but higher nuclear charge, Actinides are better complexing agents than lanthanides.

M⁴+ > MO₂²+ > M³⁺,br>

is the order in which the degree of complexion decreases.

Chemical Reactivity of Actinides

Actinides are more electropositive and reactive than lanthanides due to their lower ionization energy. They react when exposed to hot water. Form a passive coating by reacting with oxidizing agents. Halides and hydrides are formed. Actinides are especially powerful reducing agents.

Similarities between Lanthanoids and Actinoids series 

1. lanthanoids and actinoids have a high Oxidation State of +3.

2. These elements are filled with (n-2) f orbitals.

3. lanthanoids and actinoids are both reactive and electropositive.

5. As the atomic number of these elements increases, so does their ionic and atomic size.
6. Lanthanoids and actinoids both have strong magnetic characteristics.

Differences between Lanthanoids and Actinoids series

1. The filling of Lanthanides involves 4F-orbitals, whereas the filling of Actinoids involves 5F-orbitals. The energy that binds this 4F atom is smaller than that of Actinoids, which is 5F electrons. The shielding of 5F electrons is also less than that of 4F electrons.
2.  The paramagnetic characteristics of Lanthanides are fairly simple to explain. In the case of Actinides, however, it is difficult to explain all of the paramagnetic properties. Except for Promethium, the majority of Lanthanides are non-radioactive.
3.  The elements in the Actinide series are all radioactive. There are multiple oxocations of the elements in the Actinides series, but none in the Lanthanides.
4.  In contrast to the chemicals found in Lanthanides, the compounds generated by Actinides are highly basic in nature. lanthanoids and actinoids are frequently referred to as inner transition metals.

Conclusion

The Actinide series, which covers the sixth period and the third group of the periodic table, has elements with atomic numbers ranging from 89 to 103. The series is found beneath the main body of the periodic table, one row below the Lanthanide series. Rare Earth Metals include the Lanthanide and Actinide series. These elements have a wide range of oxidation values and are all radioactive. Uranium is the most prevalent and well-known element, and it is used as nuclear fuel when it is transformed into plutonium via a nuclear reaction.