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Chapter 19: Problem 5

What are transuranium elements and how are they synthesized?

Short Answer

Expert verified
Transuranium elements are chemical elements with atomic numbers greater than 92, not found naturally on Earth, and synthesized artificially in laboratories or as products in nuclear reactions. They are produced by bombarding atomic nuclei of lighter elements with charged particles such as protons, neutrons, or other atomic nuclei, creating excited compound nuclei that decay into new heavier elements. Several synthesis methods include neutron capture, proton or deuteron bombardment, and heavy-ion fusion. These elements have various applications in research, medicine, nuclear power, and other fields.

Step by step solution

01

Definition of Transuranium Elements

Transuranium elements are chemical elements with atomic numbers greater than 92. They are also called "beyond uranium" elements, as they are not found naturally in significant quantities on Earth. Many of these elements are unstable, radioactive, and have short half-lives. Since these elements do not exist naturally, they need to be synthesized artificially in laboratories or as products in nuclear reactions.
02

Synthesis of Transuranium Elements

Transuranium elements are synthesized by bombarding atomic nuclei of lighter elements with charged particles (such as protons, neutrons, or other atomic nuclei). The collisions produce excited compound nuclei that can decay into new heavier elements. These heavier elements have a higher atomic number than uranium, making them transuranium elements.
03

Examples of Synthesis Methods

There are several methods for synthesizing transuranium elements. A few examples include: 1. Neutron Capture: This method involves bombarding a target element's nucleus (such as uranium) with a neutron, causing the target nucleus to absorb the neutron and transform into another element. The newly formed element can then undergo beta decay, transforming it into a new element with a higher atomic number. 2. Proton or Deuteron Bombardment: This method involves bombarding a target nucleus with high-energy protons or deuterons (the nucleus of deuterium, a heavy isotope of hydrogen). The protons or deuterons can fuse with the target nucleus, forming a ionized nucleus that releases excess energy and transforms into a new element with a higher atomic number. 3. Heavy-ion Fusion: In this method, atomic nuclei of heavy ions are accelerated and collided with a target nucleus. Upon collision, the nuclei can fuse together, creating an unstable compound nucleus with a high atomic number. The unstable compound nucleus can then decay through various processes, including the emission of alpha, beta, or gamma radiation, and can form a new element with a higher atomic number than uranium. By choosing the appropriate synthesis method and target materials, scientists can create a variety of transuranium elements with different properties and potential applications in research, medicine, nuclear power, and other fields.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Artificial Synthesis of Elements
Understanding the artificial synthesis of elements is an essential leap into the realm of modern nuclear chemistry. Unlike natural elements that form through stellar processes, several elements beyond uranium, called transuranium elements, are not found in nature and must be fabricated in laboratory settings due to their instability and short half-lives. This requires precise and highly controlled nuclear reactions, where smaller atomic nuclei are manipulated to combine or absorb additional particles, forging new elements with greater atomic numbers.

These human-made elements are primarily used for scientific research but have also found applications in medicine, such as in the treatment of cancer, and in industry, within the construction of specialized detection equipment. The creation of such elements is not only a scientific milestone, it provides valuable insights into the behavior of atomic nuclei and helps to fill the gaps in our understanding of the periodic table.
Neutron Capture Process
The neutron capture process is one of the foundational methods in the formation of transuranium elements. It involves exposing a target element like uranium to a stream of neutrons. When a neutron collides with the nucleus of the target, it may be absorbed, resulting in a heavier isotope. This heavier isotope often undergoes a series of beta decays, where a neutron is transformed into a proton, and the atom's identity shifts up the periodic table.

For example, bombarding uranium-238 with neutrons can eventually create plutonium-239, another transuranium element. This process holds immense importance in both the natural and artificial production of heavy elements, including those involved in the functioning of nuclear reactors and the development of nuclear weapons.
Proton Bombardment Method
When scientists aim to create new elements by the proton bombardment method, they accelerate protons to high energies before colliding them with the nucleus of a target element. Upon impact, the proton may merge with the target nucleus, increasing its atomic number by one.

This method requires precise control over the energy of the protons to overcome the repulsive forces between the positively charged proton and the target nucleus. When successful, it can yield an element not previously observed in nature. For example, the proton bombardment of bismuth can result in the creation of elements like astatine. This technique is often used in particle accelerators and is key to expanding our knowledge of the outer reaches of the periodic table.
Heavy-ion Fusion Technique
Heavy-ion fusion technique is a principal method for creating superheavy elements, typically heavier than those produced by neutron capture or proton bombardment. In this technique, two heavy nuclei are accelerated to high velocities and then collided. The resulting fusion forms an incredibly unstable nucleus that usually undergoes a chain of decays by emitting alpha particles (helium nuclei) or potentially beta particles.

The elements synthesized via heavy-ion fusion can have a very brief existence, sometimes lasting only milliseconds before decaying into lighter, more stable elements. One of the noteworthy triumphs of this method was the creation of element 118, named oganesson, which is currently the heaviest element in the periodic table. Through this technique, the frontier of what is known in the atomic landscape continuously expands, challenging the limits of physical and chemical theories.

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Most popular questions from this chapter

When nuclei undergo nuclear transformations, \(\gamma\) rays of characteristic frequencies are observed. How does this fact, along with other information in the chapter on nuclear stability, suggest that a quantum mechanical model may apply to the nucleus?

Assume a constant \({ }^{14} \mathrm{C} /{ }^{12} \mathrm{C}\) ratio of \(13.6\) counts per minute per gram of living matter. A sample of a petrified tree was found to give \(1.2\) counts per minute per gram. How old is the tree? \(\left(\right.\) For \({ }^{14} \mathrm{C}, t_{1 / 2}=5730\) years. \()\)

Natural uranium is mostly nonfissionable \({ }^{238} \mathrm{U} ;\) it contains only about \(0.7 \%\) of fissionable \({ }^{235} \mathrm{U}\). For uranium to be useful as a nuclear fuel, the relative amount of \({ }^{235} \mathrm{U}\) must be increased to about \(3 \%\). This is accomplished through a gas diffusion process. In the diffusion process, natural uranium reacts with fluorine to form a mixture of \({ }^{238} \mathrm{UF}_{6}(g)\) and \({ }^{235} \mathrm{UF}_{6}(g)\). The fluoride mixture is then enriched through a multistage diffusion process to produce a \(3 \%^{235} \mathrm{U}\) nuclear fuel. The diffusion process utilizes Graham's law of effusion (see Chapter 5, Section 5.7). Explain how Graham's law of effusion allows natural uranium to be enriched by the gaseous diffusion process.

A reported synthesis of the transuranium element bohrium (Bh) involved the bombardment of berkelium-249 with neon-22 to produce bohrium-267. Write a nuclear reaction for this synthesis. The half-life of bohrium-267 is \(15.0\) seconds. If 199 atoms of bohrium-267 could be synthesized, how much time would

In 1994 it was proposed (and eventually accepted) that element 106 be named seaborgium, \(\mathrm{Sg}\), in honor of Glenn \(\mathrm{T}\). Seaborg, discoverer of the transuranium elements. a. \({ }^{263} \mathrm{Sg}\) was produced by the bombardment of \({ }^{249} \mathrm{Cf}\) with a beam of \({ }^{18} \mathrm{O}\) nuclei. Complete and balance an equation for this reaction. b. \({ }^{263} \mathrm{Sg}\) decays by \(\alpha\) emission. What is the other product resulting from the \(\alpha\) decay of \({ }^{263} \mathrm{Sg}\) ?
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