The Actinide Series comprises a group of chemical elements that span atomic numbers 89 to 103 on the periodic table. These elements are characterized by their unique electronic configurations, diverse chemical properties, and significant radioactivity. This article explores the definition, applications, properties, features a table of actinides, and discusses the challenges associated with their use.
History of the Actinides
The first actinides to be discovered were Uranium by Klaproth in 1789 and Thorium by Berezelius in 1829, but most of the Actinides were man-made products of the 20th century. Actinium and Protactinium are found in small portions in nature, as decay products of 253-Uranium and 238-Uranium. Microscopic amounts of Plutonium are made by neutron capture by Uranium, and yet occur naturally. Monazite is the principle Thorium ore. It is a phosphate ore that contains great amounts of Lanthanides in it. The main Uranium ore is U3O8 and is known as pitchblende, because it occurs in black, pitch-like masses. An example of pitchblende is located in the picture below. All elements past Uranium are man-made. Actinides require special handling, because many of them are radioactive and/or unstable. The radiation in actinides plays a large role in the chemistry and arrangement of particles in crystals.
Definition of Actinides:
The Actinide Series is named after actinium, the first element in the series, and includes all elements with atomic numbers from 89 (actinium) to 103 (lawrencium). These elements are part of the larger group of transition metals but are distinguished by the filling of their 5f orbitals. The actinides are often further divided into light actinides (thorium to uranium) and heavy actinides (neptunium to lawrencium), based on their atomic numbers and properties.
Applications:
1. Nuclear Energy:
Actinides play a crucial role in nuclear energy production. Uranium-235 and plutonium-239 are the primary fuels used in nuclear reactors. Uranium-235 undergoes fission reactions, releasing large amounts of energy, which is harnessed for electricity generation. Plutonium-239, produced as a byproduct in reactors, can also be used as fuel. Research continues on using thorium-232 as a potential alternative fuel due to its abundance and reduced proliferation risks.
2. Radioactive Dating:
Several actinides, such as uranium-238, are used in radioactive dating techniques. By measuring the decay of uranium isotopes to lead in rocks and minerals, scientists can determine the age of geological formations, providing insights into Earth’s history and the evolution of natural systems.
3. Medical and Scientific Applications:
Actinides are utilized in various scientific and medical applications. Actinium-225 and thorium-232, for example, are used in targeted alpha-particle therapies for cancer treatment. These isotopes emit alpha particles that can selectively target and destroy cancerous cells while minimizing damage to surrounding healthy tissue.
4. Fundamental Research:
Actinides are essential in fundamental research in nuclear physics, chemistry, and materials science. Their complex electronic structures and varied oxidation states make them valuable subjects for studying the behavior of heavy elements and their interactions with other substances.
Common Properties:
- All are radioactive due to instability.
- Majority synthetically made by particle accelerators creating nuclear reactions and short lasting.
- All are unstable and reactive due to atomic number above 83 (nuclear stability).
- All have a silvery or silvery-white luster in metallic form.
- All have the ability to form stable complexes with ligands, such as chloride, sulfate, carbonate and acetate.
- Many of the actinides occur in nature as sea water or minerals.
- They have the ability to undergo nuclear reactions.
- The emission of radioactivity, toxicity, pyrophoricity, and nuclear criticality are properties that make them hazardous to handle.
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Emission of Radioactivity:
- The types of radiation the elements possess are alpha, beta, gamma, as well as when neutrons are produced by spontaneous fissions or boron, beryllium, and fluorine react with alpha-particles.
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Toxicity:
- Because of their radioactive and heavy metal characteristics, they are considered toxic elements.
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Pyrophoricity:
- Many actinide metals, hydrides, carbides, alloys and other compounds may ignite at room temperature in a finely divided state, which would result from spontaneous combustion fires and spreading of radioactive contaminates.
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Nuclear Criticality:
- If fissionable materials are combined, a chain reaction could occur resulting in lethal doses of radioactivity, but it depends on chemical form, isotopic composition, geometry, size of surroundings, etc.
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- The interaction of Actinides when radioactive with different types of phosphors will produce pulses of light.
| Atomic Number | Symbol | Name |
Atomic Mass
(g/mol)
|
Oxidation States | Year Discovered | |
|---|---|---|---|---|---|---|
| 89 | Ac | Actinium | [227] | [Rn] 6d17s2 | +3 | 1899 |
| 90 | Th | Thorium | 232.04 | [Rn] 6d27s2 | +2?,+3,+4 | 1829 |
| 91 | Pa | Protactinium | 231.04 | [Rn] 5f26d17s2 | +3,+4,+5 | 1913 |
| 92 | U | Uranium | 238.03 | [Rn] 5f36d17s2 | +3,+4,+5,+6 | 1789 |
| 93 | Np | Neptunium | [237] | [Rn] 5f46d17s2 | +3,+4,+5,+6,+7 | 1940 |
| 94 | Pu | Plutonium | [244] | [Rn] 5f67s2 | +3,+4,+5,+6,+7 | 1940 |
| 95 | Am | Americium | [243] | [Rn] 5f77s2 | +3,+4,+5,+6,+7? | 1944 |
| 96 | Cm | Curium | [247] | [Rn] 5f7 6d17s2 | +3,+4,+5,+6? | 1944 |
| 97 | Bk | Berkelium | [247] | [Rn] 5f97s2 | +3,+4 | 1949 |
| 98 | Cf | Californium | [251] | [Rn] 5f107s2 | +2,+3,+4 | 1950 |
| 99 | Es | Einsteinium | [252] | [Rn] 5f117s2 | +2?,+3,+4? | 1952 |
| 100 | Fm | Fermium | [257] | [Rn] 5f127s2 | +2,+3 | 1952 |
| 101 | Md | Mendelevium | [258] | [Rn] 5f137s2 | +2,+3 | 1955 |
| 102 | No | Nobelium | [259] | [Rn] 5f147s2 | +2,+3 | 1957 |
| 103 | Lr | Lawrencium | [262] | [Rn] 5f146d17s2 | +3 | 1961 |
- [#]-mass number of the longest living isotope is given when the element has no stable nucleotides.
- (?)-oxidation state is unconfirmed
Actinides have been crucial in understanding nuclear chemistry and have provided valuable usage today, such as nuclear power. These examples illustrate their importance in understanding key concepts in nuclear chemistry and related topics.
Transition Metal:
Actinides are in the f-block of the periodic table. The electron configuration of uranium is [Rn] 5f3 6d1 7s2. The reason for this arrangement unlike other conventional electron configurations such as Na with configuration of [Ne]3s2. Results from difference in energy levels due to the fact that some orbitals fill in faster than others and explains why Actinides are transition metals. (see transition metals)
The electron configurations of the actinides are due to the following:
- The energy in the 6d orbitals is lower in energy than in the 5f orbitals.
- They fill 5f orbital, 6d orbital, then 7s orbital.
- The 5f orbitals are not shielded by the filled 6s and 6p subshells.
- There is a small energy gap between the 5fn 7s2 and 5fn-1 6d 7s2 configurations.
- The 5f orbitals do not shield each other from the nucleus effectively.
- The energies of the 5f orbital drop rapidly with increasing atomic number.
Table of Actinides:
| Atomic Number | Element | Symbol | Applications |
|---|---|---|---|
| 89 | Actinium | Ac | Medical therapies, neutron sources |
| 90 | Thorium | Th | Nuclear fuel, metal alloys |
| 91 | Protactinium | Pa | Scientific research, nuclear reactors |
| 92 | Uranium | U | Nuclear fuel, depleted uranium |
| 93 | Neptunium | Np | Research in nuclear chemistry |
| 94 | Plutonium | Pu | Nuclear weapons, reactor fuel |
| 95 | Americium | Am | Smoke detectors, gamma radiation sources |
| 96 | Curium | Cm | Scientific research, neutron sources |
| 97 | Berkelium | Bk | Research in nuclear chemistry, calibrating instruments |
| 98 | Californium | Cf | Scientific research, neutron sources |
| 99 | Einsteinium | Es | Research in nuclear physics |
| 100 | Fermium | Fm | Scientific research, neutron sources |
| 101 | Mendelevium | Md | Scientific research, nuclear chemistry |
| 102 | Nobelium | No | Research in nuclear physics |
| 103 | Lawrencium | Lr | Scientific research, nuclear chemistry |
Challenges and Problems:
Despite their significant applications, actinides pose several challenges:
1. Radioactive Waste Management:
Managing radioactive waste from spent nuclear fuel and other applications is a major challenge. Safe disposal and long-term storage solutions are essential to prevent environmental contamination and health risks.
2. Proliferation Risks:
Certain actinides, particularly plutonium-239, have proliferation risks associated with their use in nuclear weapons. International efforts are focused on non-proliferation and safeguarding nuclear materials.
3. Environmental Impact:
Mining and processing actinides, such as uranium, can have environmental impacts if not managed responsibly. Efforts are ongoing to mitigate these impacts through improved mining practices and environmental monitoring.
4. Safety Concerns:
Handling and transporting radioactive materials require strict safety protocols to protect workers, the public, and the environment from radiation exposure.
Conclusion:
the Actinide Series of elements represents a crucial group in both scientific research and industrial applications, particularly in nuclear energy and medical treatments. However, their radioactive nature necessitates careful management and poses significant challenges that require ongoing technological innovation and international cooperation. Understanding and harnessing the properties of actinides responsibly are key to their continued beneficial use while minimizing associated risks.
Practice Problems:
- Which Actinides were the first to be discovered? Which Actinides were discovered in nature? What makes the Actinides you answered in the first questions different than the rest?
- For the reaction of Actinium (III) hydroxide with hydrofluoric acid, a) write and balance the equation and b) explain what makes the O.S. of Actinium different than the other Actinides.
- Explain why isotopes, such as 241Am, 239Pu and 237Np extremely important and the main isotopes for their specific element.
- What evidence shows that Actinides are very reactive, for the most part?
- Describe what is happening during a beta particle equation.
Answers:
- The first Actinides to be discovered were Thorium and Uranium. The Actinides that were discovered in small portions in nature were Actinium and Protactinium. What makes these different from the rest is they were discovered naturally, and the Actinides all after Uranium were man-made.
- a) Ac(OH)3 +3HF+700°Cà AcF3+3H2O and b) The difference between Actinium and the other Actinides involving O.S. is Actinium only has one O.S. which is +3.
- Those specific isotopes have various but extremely high half-lives, meaning they decay slowly, which makes it easy for scientists to study and experiment with each of them over long periods of time.
- The evidence that shows Actinides are very reactive are they have low solubilities as halide compounds; and the lighter, trivalent Actinide compounds are unstable in aqueous solutions and can be easily precipitated out of acidic and basic environments.
- During a beta particle equation,a neutron within the nucleus of an atom is converted to a proton or electron spontaneously. The proton remains in the nucleus and the electron is produced as a beta particle. The extra proton causes the atomic number to increase by one unit, but the mass number is unchanged. if you want more information about difference between actindes and lanthanides series so please visite to our page.