Electronic Configuration of Actinides

• The actinide series is the elemental series in the last row of the periodic table with atomic numbers from 89 to 103.

• These elements are radioactive and have a wide range of oxidation numbers.

• Uranium is the most common and well-known element. It is used as nuclear fuel when it undergoes a nuclear reaction and converts into plutonium.

• The elements in the actinide series are radioactive, which means they emit a lot of energy during radioactive decay.

• Uranium and thorium are the most abundant actinides naturally occurring on Earth, while Plutonium is synthesised.

Electronic Configuration of Actinides

• Actinide is an element that occupies the 5th orbit of the (n2)th orbit and is also called a 5f block element.

• All the 15 components of actinides starting from Ac89 (5f0 6d1 7s2 ) to Lr103 (5f14 6d1 7s2) are classified in this series, as they all have identical tangible and composition characteristics.

• This is because actinium is considered a version of actinides.

• Actinides have the general electronic configuration [Rn] 5f0-14 6d0-1 7s2. Because the energy difference between 5f and 6d is insignificant, it is hard to estimate whether the electrons have entered the 5f or 6d orbital.

• Actinides are the second series of f-block elements. With an electronic configuration of [Rn] 5f1-14 6d 0-17s2, where Rn is the electronic configuration of the nearest noble gas, i.e., Radium.

• Because the electrons energies in the 5f and 6d orbitals are close, electrons move to the 5f orbital.

• Other elements’ 14 electrons, except for Thorium, are added to the 5f orbital. These irregularities in actinide electronic configuration result from the stability of f0, f7, and f14 occupants of the 5f orbitals.

• The electrons in the 5f orbital can bond to a greater extent also.

Elemental Table

• Valency, as shown in the stated arrangements of the actinide elements, is the electronic arrangement of actinium [Rn]5f0 6d1 7s2. After that are the fourteen actinides, the final subatomic particle to enter the 6d-subshell.

• The extra subatomic particle should enter a 5fsub-shell in the next element, Th. And this process must be repeated until the final element, Lr.

• As a result, the 6d sub-shell in each element must remain filled individually, yielding the expected valency of shell arrangements of 5f1-146d1 7s2 for these elements.

• The energy of the sub-shells (6d&5f) are nearly identical, and the elements of the atomic ranges are incredibly complicated. Recognising the orbital according to the number of protons and neutrons to jot down the arrangements is difficult.

• The valency of the electronic arrangements of the shell of the elements is very important for chemical performance. Further, the competitive factor between 5fn 6d0 7s2 and 5fn-16d1 7s2 is unique.

• Actinides’ electronic configurations do not adhere to the basic behaviour as lanthanides do. Because of the nearly equal energies of 5f and 6d, electrons in the 4 initial actinide elements, Actinium, Thorium, Protactinium, and Uranium, may occupy the 5f or 6d subshells or both.

• Except for Cm (Z=96) and Lr (Z=103), where the 6d1 electron does not shift to 5f due to stable 5f7 and 5f14 configurations, the 6d1 electron shifts to the 5f-subshell from Pu (Z=94).

• Despite belonging to the 5f-series, it is clear that Th lacks an f-electron (i.e., actinides), where both the expected and actual configurations of Pa, U, Np, Cm, and Lr are the same. In contrast to other actinides, 6d-subshell lacks a d-electron.

Oxidation State

• Actinides have different oxidation states due to the lower energy difference between the 5f, 6d, and 7s orbitals.

• Even though 3+ is the most stable oxidation state, additional oxidation states are possible due to the strong shielding of f-electrons.

• The maximum possible oxidation state rises until the middle of the series and then falls, i.e., from +4 for Th to +5, +6, and +7 for Pa, V, and Np, in the middle.

Conclusion

Actinides have radioactive properties along with a lot of energy. They also possess higher chemical reactivity and lower ionisation enthalpies.

Actinides have a 7s2 electronic configuration, with variations in the 5f and 6f subshells. As the table progresses from Th to Lr, the atomic and ionic sizes of the elements decrease.