Actinide – Radio active elements

Actinide are a series of chemical elements in the Periodic Table, which are named after the very first chemical element in the series – Actinium. They share similarities with Lanthanides in terms of chemical and physical properties, but the latter actinides are more similar to Transition Metals rather than to Lanthanides. Actinides elements are all radioactive and they mostly behave like metals. The following 15 chemical elements in the Periodic Table form the actinides series: Actinium (Ac), Thorium (Th), Protactinium (Pa), Uranium (U), Neptunium (Np), Plutonium (Pu), Americium (Am), Curium (Cm), Berkelium (Bk), Californium (Cf), Einsteinium (Es), Fermium (Fm), Mendelevium (Md), Nobelium (No), and Lawrencium (Lr). Their atomic numbers are the sequence between 89 (Actinium) and 103 (Lawrencium).


Physical Characteristics of the actinide

In terms of physical characteristics all actinides in the Periodic Table are metallic chemical elements. They are soft and some of them can even be cut with a knife. Actinide elements appear with a silverfish hue, which gets tarnished when exposed to air. Their density is relatively high and they have a good plasticity. The electrical resistivity of Actinides elements varies between 15 and 150. Their melting points and boiling points are high, but Neptunium and Plutonium have unusually low melting point. All actinide have extremely large atomic radius and ionic radius. Some of their isotopes have blue, purple, reddish, green, pinkish and yellowish hues.


Chemical Properties of the actinide

Actinide are not only radioactive, but they are also highly reactive to halogens, chalcogens, air and water. Actinide elements have a large variety of valence states and they have various oxide forms. These elements have crystalline phases and they are paramagnetic. They have the ability to combine directly with most Nonmetal elements and they form numerous allotropes.


Bonding and reaction to other elements and compounds

Actinides elements are highly reactive, especially when it comes to water and air. These Periodic elements react easily with Halogens and they form various salts. The actinides chlorides, bromides and iodides are soluble in water. Actinides, which can oxidize in a common oxidation state of +6, can form complex anions. Their aqueous solutions vary in color. They have acidic compounds and they hydrolyze. Actinides ignite spontaneously when exposed to air, which makes them pyrophoric. They are highly reactive, especially to boiling water, and they release Hydrogen. Their vigorous nuclear reaction is what makes actinides dangerous.

Actinide - Uranium roll front hosted in Dakota Sandstone                                                    Image source : Flickr

Uses and applications of the actinide

Due to their radioactivity actinide have a large application in historical and present-day nuclear science. They are also used in metallurgy, as well as in distillation systems.

Actinide elements are vastly used in nuclear science as nuclear weapons, aviation missiles, nuclear reactors, thermal reactors, and fuel. Thorium is used in the manufacturing of gas mantles, as well as in alloys with Zinc and Magnesium. Plutonium was used in the manufacturing of the infamous plutonium nuclear bombs. Uranium isotopes can be used scientifically in order to estimate the age of stars. Actinium isotopes are applicable in various industries mostly as neutron sources and also as indicators for radioactivity in various researches.


Actinide on Earth

Actinides elements in the Periodic Table do not exist in their natural state on Earth. Primordial isotopes of Plutonium, Uranium and Thorium have been found in relative abundance, but the rest of the actinide on Earth are derived from nuclear explosions and transmutation reactions in some Uranium ores. In other words, Actinide elements are actually synthetic elements produced as by-products of various nuclear tests. Uranium and Thorium are the most abundant of all Actinide elements on our planet and are found mainly in minerals and oxides, but the rest of the actinide are produced synthetically.