Actinides Guide

In the periodic table, the placement of a certain element usually decides its chemical resemblance towards the other elements around it. There are multiple classifications of the periodic table, such as alkaline metals which occupy periods 1 and 2,  metals which occupy periods 3 to 12 and nonmetals that occupy periods 13 to 18. Within the period of metals there is a series that consists of 15 metallic chemical elements with their atomic numbers ranging from 89 to 103, that starts from actinium and ends with lawrencium. 

The series receives its name from the first element of the series , actinium. Its chemical symbol An and is generally used in the discussions of actinide chemistry for  reference to any actinide. All the actinides are considered to be part of f-block elements excluding the last actinide, lawrencium, which is represented with the d-block elements. Actinium has also many times been considered to be part of the d-block elements but lawrencium has been more generally opted in the d-block by the ones who study matter.

Actinides Notes

As mentioned above, actinides meaning implies the series consisting of elements that are between the atomic number of 89 and 103. The series have mostly corresponded towards the filling of the 5f electron shell, even though at the ground state as many have an anomalous configuration that involves the filling of the 6d shell caused by the interelectronic repulsion. 

With comparisons to the lanthanides, which are also majorly f-block elements, the actinides have shown much more variable valence. All of them have very large atomic and ionic radii and they also exhibit a very unusually large range of properties physically. While actinium and the later actinides behave the same lanthanides, the elements such as thorium, protactinium, and uranium have much more resemblance towards the transition metals in their chemical properties, with neptunium and plutonium having more of an intermediate position.

All of the actinides have a radioactive nature and exhibit energy upon the phenomena of radioactive decay. Elements that are found naturally on Earth such as thorium and uranium with synthetically produced plutonium have been the most abundantly available actinides on planet Earth. These abundant elements are often used in nuclear reactors and nuclear resources weapons. Uranium and thorium have had a vast amount of uses in our current and recent histories and other actinides such as americium is used in modern smoke detectors.

From the other actinides , primordial thorium and uranium have a very substantial occurrence naturally on Earth. When uranium undergoes radioactive decay, it has a production of actinium and protactinium in traces. The elements plutonium and neptunium are rarely formed due to the transmutation reactions in uranium ores. The other elements of the actinide groups have been created by humans and are purely synthetic. Several nuclear weapons have introduced with six actinides that are heavier than plutonium into the environment; on the analysis of the debris from the aftermath of the 1952 hydrogen bomb explosion which showed the elements americium, curium, berkelium, californium, einsteiniumand fermium.

Properties of Actinides

Actinides have properties resembling that of lanthanides. The electronic shells 6d and 7s have been filled in elements actinium and thorium. The shell 5f has also been filled with an increase in their atomic number; having the 4f shell been filled in lanthanides. The very first experimental evidence for the filling of the 5f shell consisting of actinides had been derived by McMillan and Abelson in the year 1940. As being similar to lanthanides, the ionic radius of actinides too monotonically decreases with their atomic number.

All actinides that exist in nature are radioactive in nature. In fact there are no stable isotopes of actinides that exist in nature. Since actinides can easily lose electrons due to their low ionisation energy, therefore actinides have a very high electropositive nature. Due to their reactivity, actinide metals also get very easily tarnished in air. They are also pyrophoric which means that they easily react with air and spontaneously catch fire. When the actinides are present as finely divided powder then they are even more susceptible to spontaneously catching fire.

Uses of Actinides

Since actinides are very radioactive and humans are sensitive to radiation, it is very rare to find actinides in a daily life application. But even then small amounts of actinides are found in certain objects designed to make life easier. Americium is an actinide popularly used in smoke detectors that can be found in almost all places these days. One fascinating usage of actinides is in providing luminescence to glass and other crystals. Actinium is used for medical and experimental purposes usually as a neutron ray or a gamma ray source.

But the most popular uses of actinide are in the defence and energy sector. In the energy sector, actinides are chiefly used as nuclear fuel. This is because actinides very easily undergo nuclear reactions and by precisely maintaining the different conditions, a change reaction can be generated which can lead to producing more energy. Consequently this very property is also used in the defence sector where actinides are preferred in the creation of nuclear weapons. They can undergo nuclear reactions that release a tremendous amount of energy very easily.

Conclusion

Actinides are an important group of elements but humans have not been able to completely exploit them for all the resources that they offer. They are potentially the best sources to fulfil the energy needs of the future and also in helping solve other mysteries that revolve around nuclear decay and nuclear reactions.

Actinides have properties resembling that of lanthanides. The electronic shells 6d and 7s have been filled in elements actinium and thorium. The shell 5f has also been filled with an increase in their atomic number; having the 4f shell been filled in lanthanides. The very first experimental evidence for the filling of the 5f shell consisting of actinides had been derived by McMillan and Abelson in the year 1940. As being similar to lanthanides, the ionic radius of actinides too monotonically decreases with their atomic number.