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Actinium is a radioactive metallic element that is silvery in appearance. Actinium emits a blue light in the dark due to its high radioactivity. André-Louis Debierne, a French scientist, discovered actinium in 1899 after isolating it from pitchblende. In 1902, Friedrich Otto Giesel discovered actinium on his own. Actinium's chemical behaviour is comparable to that of the rare earth lanthanum. The first element in the actinide series is actinium. Actinium's 36 known isotopes are all radioactive. Ac 227 and 228 are isotopes that exist naturally and have half-lives of 21.77 years and 6.13 hours, respectively. It has 150 times the radioactivity of radium.
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Keyterms: Lanthanum, Radium, Polonium, Uranium, Radon, Bismuth, Radioactivity, Rare earth, actinium, Lead isotopes, Equilibrium
Characteristics of Actinium
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- Actinium is the first element in the actinide series.
- Actinium's chemical behaviour is comparable to that of rare earths, particularly lanthanum. Actinium is approximately 150 times more active than radium.
- There are 36 isotopes of actinium, none of which are stable. In uranium decay, actinium occurs as the isotope 227Ac.
- Actinium has many decay products, including isotope 227Ac, a beta emitter with a half-life of 21.6 years that is a decay result of 2235U. Other significant decay products include 227Th (which has a half-life of 18.5 days), 223Ra (which has a half-life of 11.4 days), and a variety of short-lived products such as radon, polonium, bismuth, polonium, and lead isotopes.
- Actinium, when in equilibrium with its decay products, is a potent generator of alpha particles. Purified actinium reaches equilibrium with its decay products after 185 days and subsequently decays for another 21.6 years, according to the half-life of 227Ac.
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Chemical Properties of Actinium
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Look at the table below for understanding chemical properties & elements of actinium:
| Particulars | Details |
|---|---|
| Group | Actinides |
| Period | 7 |
| Block | d |
| Atomic number | 89 |
| State at 20°C | Solid |
| Electron configuration | [Rn] 6d17s2 |
| Melting point | 1050°C, 1922°F, 1323 K |
| Boiling point | 3200°C, 5792°F, 3473 K |
| Density (g cm−3) | 10 |
| Relative atomic mass | [227] |
| Key isotopes | 227Ac |
| CAS number | 7440-34-8 |
Applications of Actinium
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The uses of actinium are:
- It is approximately 150 times more radioactive than radium, making it useful as a neutron source. Aside from that, it has no substantial industrial applications.
- Actinium-225 is used in medicine to generate Bi-213 in a reusable generator or as a radioimmunotherapy agent on its own.
- It is naturally found in uranium ores. It is an uncommon free element in the earth's crust. It is more commonly made in a laboratory.
- It's an important source of alpha rays.
- Ac 225 is a radiation treatment substance that is utilised in medicine.
- It has enormous significance as a neutron source since it is fifty times more radioactive than radium.
Atomic data of Actinium
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The table below shows atomic data of actinium:
| PARTICULARS | NUMERICAL INTERPRETATION |
|---|---|
| Atomic radius, non-bonded (Å) | 2.47 |
| Electron affinity (kJ mol−1) | 33.77 |
| Covalent radius (Å) | 2.01 |
| Electronegativity (Pauling scale) | 1.1 |
Occurence of Actinium
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- It is exclusively found in uranium ores in trace amounts as 227-Ac, a and emitter with a half-life of 21.773 years. A tenth of a gramme of actinium may be found in one tonne of uranium ore.
- Actinium may be found in small levels in uranium ore, although it is more often produced in milligramme quantities by neutron irradiating 226-Ra in a nuclear reactor.
- Actinium metal was created by reducing actinium fluoride with lithium vapour at temperatures ranging from 1100 to 1300-degrees Celsius.
- Actinium is made up of one radioactive isotope, the most prevalent of which is 227-Ac (100 percent natural abundance). The most stable radioisotopes are 227-Ac with a half-life of 21.773 years, 225-Ac with a half-life of 10 days, and 226-Ac with a half-life of 29.37 hours.
- All of the remaining radioactive isotopes have half-lives of less than 10 hours, with the majority having half-lives of less than 1 minute. This element has two meta states.
- After 185 days, purified actinium-227 reaches equilibrium with its decay products and subsequently decays according to its 21.773-year half-life.
Effects of Actinium
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The two types of actinium effects are:
- ENVIRONMENTAL EFFECTS-
- The advancement of nuclear technology has resulted in both large and little emissions of radioactivity into the atmosphere, land, oceans, seas, and water table, which may be found in animal, vegetable, and inanimate materials all over the world. Radiation traverses species and accumulates in the food chain, exposing additional animals and people to its harmful consequences.
- Actinium-227 is a highly radioactive element. Radioactivity harms the gene pool of all living things, producing malignancies, immune system damage, leukaemia, miscarriages, stillbirths, abnormalities, and reproductive issues. Furthermore, radiation-induced genetic damage accumulates through lives and generations.
- HEALTH EFFECTS-
- Actinium-227 is about equivalent to plutonium in terms of hazard. Even ingesting trace amounts of actinium-227 would pose a significant health risk. Radioactivity's biggest threat to life as we know it is harm to the gene pool, or the genetic make-up of all living species. Radiation exposure causes genetic harm that accumulates across lifetimes and generations.
- After prolonged exposure, even low-dose exposures are carcinogenic. Cancers, immune system damage, leukaemia, miscarriages, stillbirths, deformities, and fertility issues may befall the current generation and all that follow. While many of these health issues are on the rise, individuals are unable to demonstrate either increase in the "background." Only epidemiological evidence can be used to infer cause in a scientifically sound manner. Perhaps the most extreme long-term result would be the complete loss of the ability to reproduce. Sterility is known to be caused by radiation.
Things to Remember
- Actinium is a radioactive element with the periodic table atomic number 89.
- It resembles metallic silver in appearance.
- In nature, it may be found in traces in the majority of Uranium ores.
- By its high radioactivity, this metal glows blue in the dark.
- It also has characteristics that are comparable to those of lanthanum.
- This radioactive element combines with oxygen to create actinium oxide, a white coating-like material. As a result, the metal is not further oxidised.
- When maintained in a solution, actinium ions look colourless. It is one of the most powerful radioactive elements.
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Sample Questions
Ques: Where can you find actinium in nature? (1 Mark)
Ans: Actinium is naturally found in uranium ores. It is an uncommon free element in the earth's crust. It is more often manufactured in laboratories, primarily for use as a radiation source.
Ques: Actinium is a member of which family? (1 Mark)
Ans: Actinium is the third element in Row 7 of the periodic table, which depicts how the chemical elements are linked to one another. Some chemists group it alongside scandium and yttrium in Group 3 (IIIB). Other chemists refer to it as the first actinide.
Ques: Is actinium poisonous? (1 Mark)
Ans: There is no known biological function for actinium. Because of its radioactivity, it is poisonous. The neutron bombardment of radium-226 produces actinium for scientific purposes. Actinium may also be found naturally in uranium ores.
Ques: What causes actinium to glow? (1 Mark)
Ans: The metal actinium is a silvery-white metal. It is sufficiently radioactive that visible samples of it glow a pale blue colour in the dark as a result of its radioactivity stimulating the air around it.
Ques: Is actinium D one of the block elements? (1 Mark)
Ans: Lanthanum and actinium are d-block elements (Myers, Oldham, & Tocci 2004, p. 130) and are commonly referred to as lanthanides and actinides (the rest of which occupy the f-block).
Ques: Is actinium a reactive element? (1 Mark)
Ans: Actinium, a soft, silvery-white radioactive metal, reacts quickly with oxygen and moisture in the air, creating a white covering of actinium oxide that inhibits further oxidation.
Ques: Is actinium considered a transition metal? (1 Mark)
Ans: The naturally occurring element actinium (Ac) and the artificially manufactured elements rutherfordium (Rf), dubnium (Db), seaborgium (Sg), bohrium (Bh), hassium (Hs), meitnerium (Mt), darmstadtium (Ds), roentgenium (Rg), and the as-yet unidentified ununbium comprise the period 7 transition metals (Uub).
Ques: Why is it so difficult to separate actinides? (1 Mark)
Ans: The significantly higher quantity of neutron-absorbing lanthanides in spent fuel, along with their very similar chemistry to actinides, makes separation extremely challenging.
Ques: What is the source of all actinides' radioactivity? (1 Mark)
Ans: The actinide elements' radioactivity is produced by their nuclear instability. The nucleus of an actinide material undergoes radioactive decay to become more stable, producing gamma rays, alpha particles, beta particles, or neutrons.
Ques: What does Actinium react with? (2 Marks)
Ans: Actinium emits a blue glow when exposed to light and interacts with water to create hydrogen gas. It also interacts with air, acids, and bases, but not bases. It is employed in thermoelectric power sources as well as neutron emitters. The half-life of actinium's most stable isotope is 21.8 years.
Ques: Why are actinides Coloured? (2 Marks)
Ans: The colour is caused by an electrical transition in the 5f levels. Actinide electronic transitions are approximately 10 times more intense than lanthanide transitions. The discrepancy is due to 4f and 5f electron differences.
Ques: Are actinides created by humans? (2 Marks)
Ans: The actinides are the 15 elements with atomic numbers ranging from 89 to 103. With a few exceptions, such as uranium and thorium, the actinides category consists primarily of man-made elements. The actinides are best known for the elements uranium and plutonium, which are utilised in nuclear reactors and nuclear weapons, respectively.
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