Actinides are elements with atomic numbers from 90 to 103 following the element Actinium. They include naturally occurring elements such as uranium, protactinium and thorium. Also, there are eleven elements of transuranic that are created by the artificial processes of nuclear energy. Actinium is known to be radioactive.

The series of actinides got its name from the very first element of the series that is actinium. The starting word (An) in the actinide series of elements is used in referring to the other elements of the same series as they consist of the range of atomic numbers from 90 to 103, which reflects on the periodic table. These elements are considered as radioactive in nature. Naturally occurring elements of actinide on earth are uranium and thorium which are numerous in numbers. On the other hand, plutonium is known to be synthesised.

Physical properties of actinides

• There is no presence of stable isotopes among these elements and they are radioactive in nature.
• Actinides are popularly known to be strong in electro positivity. 
• There are some non-metal substances which quickly dissolve with actinides.
• These metals smudge very quickly in the air. They are pyrophoric in nature, which means that they quickly burn out in the air, especially when dispersed in the powdered form.
• These are the metals which are very dense and have a unique type of structure.
• There is plutonium, which is formed by the combination of the 6 allotropes.
• These are the soft form of metals and can easily be cut with a knife. By nature, they are malleable and ductile.
• Actinides often produce hydrogen. This happens when they react with hot water. These are all paramagnetic.

Chemical properties of actinides

• There are some actinides like lanthanides which are highly halogens and chalcogens reactive.
• Both lanthanum and actinium are known as chemically relatable.
• Among all, thorium is considered as an element which is chemically active. There is another variety of thorium, tetravalent compounds, and they are usually colourless, due to low electrons.
• Lanthanum, a form of actinium, has very little reactivity and its basic characteristics are very strong.

Chemical reactivity of actinides

Actinides are considered to be electropositive and are more reactive as compared to lanthanides because they are less ionised in energy. When actinides are exposed to hot water, they start reacting. They usually get a passive kind of coating after reacting with some oxidising substance. After that, hydrides and halides occur. Actinides are the best example of effective lowering agents.

All actinides are considered to be very high in density, only americium and thorium are not. Lanthanides are one of the actinides, which have a much higher melting point than others, but no boiling temperature.

Some applications and uses of Actinides

• In smoke detectors, americium and some other actinides are utilized. In gas mantles, thorium is the only single element that is working.
• For conducting scientific research and study, scientists usually use actinium.
• Actinium also works as an indicator, a source of gamma and a source of neutrons.
• In defensive activities, such as nuclear weapons and energy generation, a substantial number of actinides is used.
• In nuclear power plants many actinides’ elements work also in the electronic power creation. In nuclear bomb and nuclear reactors, plutonium acts as a nuclear reactor.

Conclusion

Actinides are elements with atomic numbers from 90 to 103 following element Actinium. They include naturally occurring elements such as uranium, protactinium and thorium.

These metals smudge very quickly in air. They are pyrophoric in nature, which means they quickly burn out in air, especially when dispersed in the powdered form. Among all actinides, thorium is considered as an element which is chemically active. There is another variety of thorium, tetravalent compounds, and they are usually colourless, due to low electrons. Lanthanum, a form of actinium, has very little reactivity and its basic characteristics are very strong.