What are transuranium elements and how are they synthesized?

Transuranium elements are elements that have atomic numbers greater than 92, which is the atomic number of uranium. These elements are not found naturally on Earth and need to be synthesized in laboratories or nuclear reactors. Some examples of transuranium elements include neptunium, plutonium, americium, and curium.

There are several methods used to synthesize transuranium elements. Most of them involve bombarding target elements (usually heavy elements) with small particles like neutrons, protons, or other ions. The three most common techniques used for synthesizing transuranium elements are neutron capture, proton-induced reactions, and heavy-ion induced reactions.

In the process of neutron capture, target nuclei capture slow-moving (thermal) neutrons and subsequently undergo beta decay, resulting in the formation of a new element with a higher atomic number. This process is responsible for the synthesis of the actinides like neptunium, plutonium, americium, and curium. For example, plutonium-239 can be synthesized by capturing neutrons in uranium-238, followed by beta decay: \[ {}^{238}_{92}U + {}^{1}_{0}n \rightarrow {}^{239}_{92}U \rightarrow {}^{239}_{93} Np + {}^{0}_{-1}\beta \] \[ {}^{239}_{93} Np \rightarrow {}^{239}_{94} Pu + {}^{0}_{-1}\beta \]

In proton-induced reactions, target elements are bombarded with high-energy protons, causing nuclear reactions that result in the formation of new elements. One common reaction is the (p, n) reaction, in which a proton is absorbed and a neutron is emitted. This method is used to produce elements in the transactinide range, such as berkelium and fermium.

Heavy-ion induced reactions involve bombarding target elements with heavy ions such as carbon, oxygen, or calcium. These reactions typically result in the fusion of the target nucleus and the projectile nucleus, producing heavier elements. This method is commonly used to synthesize superheavy elements, such as element 118, oganesson: \[ {}^{249}_{98}Cf + {}^{48}_{20}Ca \rightarrow {}^{294}_{118}Og + 3{}^{1}_{0}n \] In summary, transuranium elements are those with atomic numbers greater than 92 and are synthesized using various methods, including neutron capture, proton-induced reactions, and heavy-ion induced reactions. These elements do not occur naturally on Earth and are usually produced in laboratories or nuclear reactors.