Einsteinium (99)

Einsteinium is radioactive rare earth metal named after Albert Einstein. It is of no commercial importance and only a few of its compounds are known.

Name: Einsteinium Symbol: Es Atomic number: 99 Atomic weight: [ 252 ] Standard state: solid at 298 K CAS Registry ID: 7429-92-7

Group name: Actinoid Period in periodic table: 7 (actinoid) Block in periodic table: f-block Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic

Historical information

Einsteinium was discovered by Workers at Argonne, Los Alamos, USA, and the University of California at Berkeley at 1952 in USA. Origin of name: named after "Albert Einstein".

Einsteinium was identified by Ghiorso and others (Berkeley, California, USA) in 1952 in radioactive debris from the first large thermonuclear bomb explosion, which took place in the Pacific in November 1952. In 1961, a sufficient amount of einsteinium was produced to permit separation of a macroscopic amount of ²⁵³Es.

Einsteinium was discovered as a component of the debris of the first hydrogen bomb explosion in 1952. Its most common isotope einsteinium-253 (half-life 20.47 days) is produced artificially from decay of californium-253 in a few dedicated high-power nuclear reactors with a total yield on the order of one milligram per year. The reactor synthesis is followed by a complex procedure of separating einsteinium-253 from other actinides and products of their decay. Other isotopes are synthesized in various laboratories, but at much smaller amounts, by bombarding heavy actinide elements with light ions. Owing to the small amounts of produced einsteinium and the short half-life of its most easily produced isotope, there are currently almost no practical applications for it outside of basic scientific research. In particular, einsteinium was used to synthesize, for the first time, 17 atoms of the new element mendelevium in 1955.

In their discovery of the elements 99 and 100, the American teams had competed with a group at the Nobel Institute for Physics, Stockholm, Sweden. In late 1953 – early 1954, the Swedish group succeeded in the synthesis of light isotopes of element 100, in particular ²⁵⁰Fm, by bombarding uranium with oxygen nuclei. These results were also published in 1954. Nevertheless, the priority of the Berkeley team was generally recognized, as its publications preceded the Swedish article, and they were based on the previously undisclosed results of the 1952 thermonuclear explosion; thus the Berkeley team was given the privilege to name the new elements. As the effort which had led to the design of Ivy Mike was codenamed Project PANDA, element 99 had been jokingly nicknamed "Pandamonium" but the official names suggested by the Berkeley group derived from two prominent and recently deceased scientists, Albert Einstein (died 18 April 1955) and Enrico Fermi (died 28 November 1954):

"We suggest for the name for the element with the atomic number 99, einsteinium (symbol E) after Albert Einstein and for the name for the element with atomic number 100, fermium (symbol Fm), after Enrico Fermi."

The discovery of these new elements was announced by Albert Ghiorso at the first Geneva Atomic Conference held on 8–20 August 1955. The symbol for einsteinium was first given as "E" and later changed to "Es" by IUPAC (International Union of Pure and Applied Chemistry)

Physical properties

• Melting point: 1133 [or 860 °C (1580 °F)] K
• Boiling point: no data K
• Density of solid: 13500 kg m^-3

Einsteinium is a soft, silvery, paramagnetic metal. Its chemistry is typical of the late actinides, with a preponderance of the +3 oxidation state; the +2 oxidation state is also accessible, especially in solids. The high radioactivity of einsteinium-253 produces a visible glow and rapidly damages its crystalline metal lattice, with released heat of about 1000 watts per gram. Difficulty in studying its properties is due to einsteinium-253's conversion to berkelium and then californium at a rate of about 3% per day. The isotope of einsteinium with the longest half-life, einsteinium-252 (half-life 471.7 days) would be more suitable for investigation of physical properties, but it has proven far more difficult to produce and is available only in minute quantities, and not in bulk. Einsteinium is the element with the highest atomic number which has been observed in macroscopic quantities in its pure form, and this was the common short-lived isotope einsteinium-253

Orbital properties

• Ground state electron configuration:  [Rn].5f¹¹.7s²
• Shell structure:  2.8.18.32.29.8.2
• Term symbol:   ⁵I_15/2
• Pauling electronegativity: 1.3 (Pauling units)
•  First ionization energy: 619 kJ mol^-1
• Second ionization energy: no data kJ mol^-1

Neptunium (93)

And now for something completely different ;') The synthetic elements!
Starting with the sea god's element: Neptunium!


Neptunium is a radioactive rare earth metal and has at least 3 allotropic forms. It is named for the planet Neptune. Np-237 is a by-product from nuclear reactors.


•Name: Neptunium
•Symbol: Np
•Atomic number: 93
•Atomic weight: [ 237 ] 
•Standard state: solid at 298 K
•CAS Registry ID: 7439-99-8
•Group in periodic table: 
•Group name: Actinoid
•Period in periodic table: 7 (actinoid)
•Block in periodic table: f-block
•Color: silvery metallic
•Classification: Metallic


Historical information
Neptunium was discovered by Edwin M. McMillan and P. H. Abelson at 1940 in USA, at Berkeley, California, who bombarded uranium with neutrons produced from a cyclotron.. Named after the planet Neptune, neptunium was the first synthetic transuranium element of the actinide series. It was discovered by McMillan and Abelson in 1940 It was the first synthetic transuranium (elements after uranium) element discovered.


Physical properties 
•Melting point: 910 [or 637 °C (1179 °F)] K
•Boiling point: 4300 [or ca. 4000 °C (7232 °F)] K
•Density of solid: 20450 kg m-3


Orbital properties
•Ground state electron configuration: [Rn].5f4.6d1.7s2
•Shell structure: 2.8.18.32.22.9.2
•Term symbol: 6L11/2

Californium (98)

Californium is a radioactive rare earth metal named after the state of California and the University of California (USA). Californium-252 is a strong neutron emitter and one microgram emits 170 million neutrons per minute, making it a biological hazard. It has a few specialized uses but only a few of its compounds are known.

Name: Californium Symbol: Cf Atomic number: 98 Atomic weight: [ 251 ] Standard state: solid at 298 K CAS Registry ID: 7440-71-3

Group in periodic table: Group name: Actinoid Period in periodic table: 7 (actinoid) Block in periodic table: f-block Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic

Historical information

Californium was discovered by Glenn T. Seaborg, Stanley G. Thompson, Albert Ghiorso, and Kenneth Street at 1950 in USA. The element was named after the State and University of "California.”.

The element was first made at the University of California, Berkeley, in 1950 by bombarding curium with alpha particles (helium-4 ions). It is an actinide element, the sixth trans-uranium element to be synthesized, and has the second-highest atomic mass of all the elements that have been produced in amounts large enough to see with the unaided eye (after einsteinium). The element was named after California and the University of California. It is the heaviest element to occur naturally on Earth; heavier elements can only be produced by synthesis.

Weighable quantities of californium were first produced by the irradiation of plutonium targets at the Materials Testing Reactor at the Idaho National Laboratory; and these findings were reported in 1954. The high spontaneous fission rate of californium-252 was observed in these samples. The first experiment with californium in concentrated form occurred in 1958. The isotopes californium-249 to californium-252 were isolated that same year from a sample of plutonium-239 that had been irradiated with neutrons in a nuclear reactor for five years. Two years later, in 1960, Burris Cunningham and James Wallman of the Lawrence Radiation Laboratory of the University of California created the first californium compounds—californium trichloride, californium oxychloride, and californium oxide—by treating californium with steam and hydrochloric acid.

The High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee, started producing small batches of californium in the 1960s. By 1995, the HFIR nominally produced 500 milligrams of californium annually. Plutonium supplied by the United Kingdom to the United States under the 1958 US-UK Mutual Defense Agreement was used for californium production.

The Atomic Energy Commission sold californium-252 to industrial and academic customers in the early 1970s for $10 per microgram and an average of 150 mg of californium-252 were shipped each year from 1970 to 1990. Californium metal was first prepared in 1974 by Richard G. Haire and Russell D. Baybarz who reduced californium(III) oxide with lanthanum metal to obtain microgram amounts of sub-micrometer thick films

Physical properties

• Melting point: 1173 [or 900 °C (1652 °F)] K
• Boiling point: 1745 K
• Density of solid: 15100 kg m^-3

·         Below 51 K (−220 °C) californium metal is either ferromagnetic or ferrimagnetic (it acts like a magnet)

·         Between 48 and 66 K it is antiferromagnetic (an intermediate state)

·         Above 160 K (−110 °C) it is paramagnetic (external magnetic fields can make it magnetic).

Orbital properties

• Ground state electron configuration:  [Rn].5f¹⁰.7s²
• Shell structure:  2.8.18.32.28.8.2
• Term symbol:   ⁵I₈
• Pauling electronegativity: 1.3 (Pauling units)
• First ionization energy: 608 kJ mol^-1
• Second ionization energy: no data kJ mol^-1

Uses

·         Californium-252 (half-life of 2.645 years) is produced in nuclear reactors and has found a variety of uses.

·         It is used as a neutron emitter, providing neutrons for the start-up of nuclear reactors.

·         It has also been used as a target material for producing transcalifornium elements. Ununoctium, the heaviest of the elements, was produced when a californium target was bombarded with calcium ions.

·         Californium-252 is used in to treat cervical cancer. It is also used to analyze the sulfur content of petroleum and in neutron moisture gauges to measure the moisture content of soil.

Abundance and Isotopes

·         Abundance in the earth’s crust: none

·         Abundance in the solar system: negligible

·         Source: Californium is a synthetic element and is not found naturally on Earth. The spectrum of californium-254 has been observed in supernovae. Californium is produced in nuclear reactors by bombarding plutonium with neutrons and in particle accelerators.

·         Isotopes: Californium has 20 isotopes whose half-lives are known, with mass numbers 237 to 256. Californium has no naturally occurring isotopes. Its longest lived isotopes are ²⁵¹Cf, with a half-life of 898 years, ²⁴⁹Cf with a half-life of 351 years and ²⁵⁰Cf with a half-life of 13.08 years

Berkelium (97)

Berkelium is a radioactive rare earth metal, named after the University of California at Berkeley (USA). Apparently, berkelium tends to accumulate in the skeletal system. It is of no commercial importance and only a few of its compounds are known.

Name: Berkelium Symbol: Bk Atomic number: 97 Atomic weight: [ 247 ] Standard state: solid at 298 K CAS Registry ID: 7440-40-6

Group name: Actinoid Period in periodic table: 7 (actinoid) Block in periodic table: f-block Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic

Historical information

Although very small amounts of berkelium were possibly produced in previous nuclear experiments, it was first intentionally synthesized, isolated and identified in December 1949 by Glenn T. Seaborg, Albert Ghiorso and Stanley G. Thompson. They used the 60-inch cyclotron at the University of California, Berkeley. Similar to the nearly simultaneous discovery of americium (element 95) and curium (element 96) in 1944, the new elements berkelium and californium (element 98) were both produced in 1949–1950.

The name choice for element 97 followed the previous tradition of the Californian group to draw an analogy between the newly discovered actinide and the lanthanide element positioned above it in the periodic table. Previously, americium was named after a continent as its analogue europium, and curium honored scientists Marie and Pierre Curie as the lanthanide above it, gadolinium, was named after the explorer of the rare earth elements Johan Gadolin. Thus the discovery report by the Berkeley group reads: "It is suggested that element 97 be given the name berkelium (symbol Bk) after the city of Berkeley in a manner similar to that used in naming its chemical homologue terbium (atomic number 65) whose name was derived from the town of Ytterby, Sweden, where the rare earth minerals were first found." This tradition ended on berkelium, though, as the naming of the next discovered actinide, californium, was not related to its lanthanide analogue dysprosium, but after the discovery place.

The most difficult steps in the synthesis of berkelium were its separation from the final products and the production of sufficient quantities of americium for the target material. First, americium (²⁴¹Am) nitrate solution was coated on a platinum foil, the solution was evaporated and the residue converted by annealing to americium dioxide (AmO₂). This target was irradiated with 35 MeV alpha particles for 6 hours in the 60-inch cyclotron at the Lawrence Radiation Laboratory, University of California, Berkeley. The (α,2n) reaction induced by the irradiation yielded the ²⁴³Bk isotope and two free neutrons

The first visible amounts of a pure berkelium compound, berkelium chloride, were produced in 1962, and weighed just 3 billionth of a gram (3.0 x 10^-10 g or 0.0000000003 g). Very, very tiny!

Physical properties

• Melting point: 1259 [or 986 °C (1807 °F)] K
• Boiling point: no data K
• Density of solid: 14780 kg m^-3

Orbital properties

• Ground state electron configuration:  [Rn].5f⁹.7s²
• Shell structure:  2.8.18.32.27.8.2
• Term symbol:   ⁶H_15/2
• Pauling electronegativity: 1.3 (Pauling units)
•  First ionization energy: 601 kJ mol^-1
•  Second ionization energy: no data kJ mol^-1

Occurrence

All berkelium isotopes have a half-life far too short to be primordial (existing in original form since before the formation of the Earth). Thusly, all primordial berkelium has decayed by now and any present on the planet has been created in laboratory.
On Earth, berkelium is mostly concentrated in certain areas, which were used for the atmospheric nuclear weapons tests between 1945 and 1980, as well as at the sites of nuclear incidents, such as the Chernobyl disaster, Three Mile Island accident and 1968 Thule Air Base B-52 crash. The first US hydrogen bomb, a 62 ton fusion bomb (code name Ivy Mike), was tested at the Enewetak Atoll on 1 November, 1952. Analysis of the testing site debris revealed high concentrations of various actinides, including berkelium. For reasons of military secrecy, this result was published only in 1956.
Nuclear reactors produce mostly, among the berkelium isotopes, berkelium-249. During the storage and before the fuel disposal, most of it beta decays to californium-249. The latter has a half-life of 351 years, which is relatively long when compared to the other isotopes produced in the reactor, and is therefore undesirable in the disposal products.
A few atoms of berkelium can be produced by neutron capture reactions and beta decay in very highly concentrated uranium-bearing deposits, thus making it the rarest naturally occurring element.

Health Issues

Little is known about the effects of berkelium on human body, and analogies with other elements may not be drawn because of different radiation products (electrons for berkelium and alpha particles, neutrons, or both for most other actinides). The low energy of electrons emitted from berkelium-249 is less than 126 keV, (kiloelectonVolt- a unit of energy equal to approximately 1.6 × 10 −19 J) hinders its detection due to signal interference with other decay processes, but also makes this isotope relatively harmless to humans as compared to other actinides. However, berkelium-249 transforms with a half-life of only 330 days to the strong alpha-emitter californium-249, which is rather dangerous and has to be handled in a glove box in a dedicated laboratory.
Most available berkelium toxicity data originate from research on animals. Upon ingestion by rats, only about 0.01% berkelium ends in the blood stream. From there, about 65% goes to the bones, where it remains for about 50 years, 25% to the lungs (biological half-life about 20 years), 0.035% to the testicles or 0.01% to the ovaries where berkelium stays indefinitely. The balance of about 10% is excreted. In all these organs berkelium might promote cancer, and in the skeletal system its radiation can damage red blood cells. The maximum permissible amount of berkelium-249 in the human skeleton is 0.4 nanograms.

Curium (96)

Curium

Curium [KYOOR-ee-um] is a hard, brittle, radioactive silvery metal. It does not occur in nature and must be made in a nuclear reactor by neutron capture reactions from plutonium and americium isotopes. It tarnishes slowly in dry air at room temperature.

Most compounds of Cm(III) are faintly yellow. If curium enters the body it accumulates in the bones, and is therefore very toxic as its radiation destroys the red-cell forming mechanism. Curium is a radioactive rare earth metal. The most stable isotope is ²⁴⁷Cm which has a half-life of 16 million years. Curium is probably present in uranium ores. It has a few specialized uses but only a few of its compounds are known.

Name: Curium Symbol: Cm Atomic number: 96 Atomic weight: [ 247 ] Standard state: solid at 298 K CAS Registry ID: 7440-51-9

Group name: Actinoid Period in periodic table: 7 (actinoid) Block in periodic table: f-block Color: silver Classification: Metallic

Historical information

Curium was discovered by Glenn T. Seaborg, Ralph A. James, Albert Ghiorso at 1944 in USA (Berkley again!). Origin of name comes from the pair Pierre and Marie "Curie" – discoverers of Radium.

Curium was identified by Seaborg and others in 1944 as a result of helium ion bombardment of the plutonium isotope ²³⁹Pu with α-particles.  This was then sent to the Metallurgical Laboratory at the University of Chicago where a tiny sample of curium was eventually separated and identified. However, news of the new element was not disclosed until after the end of World War II. Most unusually, it was first revealed by Seaborg when he appeared as the guest scientist on a radio show for children on 11 November 1945. It was officially announced the following week.Three years later visible amounts of the hydroxide were isolated in visible quantities as the hydroxide, Cm(OH)₃,by Werner and Perlman. In 1951, the same workers prepared curium in its elemental form for the first time.

Physical properties

• Melting point: 1613 [or 1340 °C (2444 °F)] K
• Boiling point: 3383 [or 3110 °C (5630 °F)] K
• Density of solid: 13510 kg m^-3

Orbital properties

• Ground state electron configuration:  [Rn].5f⁷.6d¹.7s²
• Shell structure:  2.8.18.32.25.9.2
• Term symbol:   ⁹D₂
• Pauling electronegativity: 1.3 (Pauling units)
•  First ionisation energy: 581 kJ mol^-1
•  Second ionisation energy: no data kJ mol^-1

Since only milligram amounts of curium have ever been produced, there are currently no commercial applications for it, although it might be used in radioisotope thermoelectric generators in the future. Curium is primarily used for basic scientific research.

Scientists have produced several curium compounds. They include: curium dioxide (CmO₂), curium trioxide (Cm₂O₃), curium bromide (CmBr₃), curium chloride (CmCl₃), curium chloride (CmCl₃), curium tetrafluoride (CmF₄) and curium iodide (CmI₃). As with the element, the compounds currently have no commercial applications and are primarily used for basic scientific research.

Americium (95)

The luster of freshly prepared americium metal is whiter and more silvery than plutonium or neptunium prepared in the same manner. Americium is a component of the smoke detector above.

Americium appears to be more malleable than uranium or neptunium and americium tarnishes slowly in dry air at room temperature. Americium is a radioactive rare earth metal which must be handled with care to avoid contact, since it is a heavy α and γ emitter. It is named after America. The α activity of 241Am is about three times that of radium. Americium is available to qualified users in the UK and in the USA.

•Name: Americium
•Symbol: Am
•Atomic number: 95
•Atomic weight: [ 243 ]
•Standard state: solid at 298 K
•CAS Registry ID: 7440-35-9
•Group in periodic table:
•Group name: Actinoid
•Period in periodic table: 7 (actinoid)
•Block in periodic table: f-block
•Color: silvery white
•Classification: Metallic

Historical informationAlthough americium was likely produced in previous nuclear experiments, it was first intentionally synthesized, isolated and identified in late autumn 1944, at the University of California, Berkeley, by Glenn T. Seaborg, Leon O. Morgan, Ralph A. James, and Albert Ghiorso. They used a 60-inch cyclotron at the University of California, Berkeley. The element was chemically identified at the Metallurgical Laboratory (now Argonne National Laboratory) of the University of Chicago. Following the lighter neptunium, plutonium, and heavier curium, americium was the fourth transuranium element to be discovered. At the time, the periodic table had been restructured by Seaborg to its present layout, containing the actinide row below the lanthanide one. This led to americium being located right below its twin lanthanide element europium; it was thus by analogy named after another continent, America: "The name americium (after the Americas) and the symbol Am are suggested for the element on the basis of its position as the sixth member of the actinide rare-earth series, analogous to europium, Eu, of the lanthanide series."

The new element was isolated from its oxides in a complex, multi-step process. First plutonium-239 nitrate (²³⁹PuNO₃) solution was coated on a platinum foil of about 0.5 cm² area, the solution was evaporated and the residue was converted into plutonium dioxide (PuO₂) by annealing. After cyclotron irradiation, the coating was dissolved with nitric acid, and then precipitated as the hydroxide using concentrated aqueous ammonia solution. The residue was dissolved in perchloric acid. Further separation was carried out by ion exchange, yielding a certain isotope of curium. The separation of curium and americium was so painstaking that those elements were initially called by the Berkeley group as pandemonium (from Greek for all demons or hell) and delirium (from Latin for madness) * and now you have some extra Greek and Latin word knowledge for free!*

Physical properties
•Melting point: 1449 [or 1176 °C (2149 °F)] K
•Boiling point: 2880 [or 2607 °C (4725 °F)] K
•Density of solid: 13780 kg m-3

Orbital properties
•Ground state electron configuration:  [Rn].5f7.7s2
•Shell structure:  2.8.18.32.25.8.2
•Term symbol:   8S7/2
•Pauling electronegativity: 1.3 (Pauling units)
• First ionization energy: 578 kJ mol-1
• Second ionization energy: no data kJ mol-1

Occurrence

Americium was detected in the fallout from the Ivy Mike nuclear test.

The longest-lived and most common isotopes of americium, ²⁴¹Am and ²⁴³Am, have half-lives of 432.2 and 7,370 years, respectively. Therefore, all primordial americium (americium that was present on Earth during its formation) should have decayed by now.

Existing americium is concentrated in the areas used for the atmospheric nuclear weapons tests conducted between 1945 and 1980, as well as at the sites of nuclear incidents, such as the Chernobyl disaser. For example, the analysis of the debris at the testing site of the first U.S. hydrogen bomb, Ivy Mike, (1 November 1952, Enewetak Atoll), revealed high concentrations of various actinides including americium; due to military secrecy, this result was published only in 1956. Trinitite, the glassy residue left on the desert floor near Alamogordo, New Mexico, after the plutonium-based Trinity nuclear bomb test on 16 July 1945, contains traces of americium-241. Elevated levels of americium were also detected at the crash site of a US B-52 bomber, which carried four hydrogen bombs, in 1968 in Greenland.

In other regions, the average radioactivity of surface soil due to residual americium is only about 0.01 picocuries/g. Atmospheric americium compounds are poorly soluble in common solvents and mostly adhere to soil particles. Soil analysis revealed about 1,900 times higher concentration of americium inside sandy soil particles than in the water present in the soil pores; an even higher ratio was measured in loam soils.

Americium is produced mostly artificially in small quantities, for research purposes. A tonne (unit of mass equal to 1,000 kilograms (2,204.6 pounds)) of spent nuclear fuel contains about 100 grams of various americium isotopes, mostly ²⁴¹Am and ²⁴³Am. Their prolonged radioactivity is undesirable for the disposal, and therefore americium, together with other long-lived actinides, has to be neutralized. The associated procedure may involve several steps, where americium is first separated and then converted by neutron bombardment in special reactors to short-lived nuclides. This procedure is well known as nuclear transmutation, but it is still being developed for americium.

Synthesis and extractionIsotope nucleosyntheses:

Americium has been produced in small quantities in nuclear reactors for decades, and kilograms of its ²⁴¹Am and ²⁴³Am isotopes have been accumulated by now. Nevertheless, since it was first offered for sale in 1962, its price, about 1,500 USD per gram of ²⁴¹Am, remains almost unchanged owing to the very complex separation procedure.  The heavier isotope, ²⁴³Am, is produced in much smaller amounts; it is thus more difficult to separate, resulting in a higher cost of the order 100,000–160,000 USD/g.

Americium is not synthesized directly from uranium – the most common reactor material – but from the plutonium isotope ²³⁹Pu. The plutonium present in spent nuclear fuel contains about 12% of ²⁴¹Pu. Because it spontaneously converts to ²⁴¹Am, ²⁴¹Pu can be extracted and may be used to generate further ²⁴¹Am. However, this process is rather slow: half of the original amount of ²⁴¹Pu decays to ²⁴¹Am after about 15 years, and the ²⁴¹Am amount reaches a maximum after 70 years.

The obtained ²⁴¹Am can be used for generating heavier americium isotopes by further neutron capture inside a nuclear reactor. Americium-242 has a half-life of only 16 hours, which makes its further up-conversion to ²⁴³Am, extremely inefficient.

Health concerns

As a highly radioactive element, americium and its compounds must be handled only in an appropriate laboratory under special arrangements. Although most americium isotopes predominantly emit alpha particles which can be blocked by thin layers of common materials, many of the daughter products emit gamma-rays and neutrons which have a long penetration depth.

If consumed, americium is excreted within a few days and only 0.05% is absorbed in the blood. From there, roughly 45% of it goes to the liver and 45% to the bones, and the remaining 10% is excreted. The uptake to the liver depends on the individual and increases with age. In the bones, americium is first deposited over cortical and trabecular surfaces and slowly redistributes over the bone with time. The biological half-life of ²⁴¹Am is 50 years in the bones and 20 years in the liver, whereas in the gonads (testicles and ovaries) it remains permanently; in all these organs, americium promotes formation of cancer cells as a result of its radioactivity.

Americium often enters landfills from discarded smoke detectors. The rules associated with the disposal of smoke detectors are relaxed in most jurisdictions. In the U.S., the "Radioactive Boy Scout" David Hahn was able to concentrate americium from smoke detectors after managing to buy a hundred of them at remainder prices and also stealing a few. There have been cases of humans being contaminated with americium, the worst case being that of Harold McCluskey, who at the age of 64 was exposed to 500 times the occupational standard for americium-241 as a result of an explosion in his lab. McCluskey died at the age of 75, not as a result of exposure, but of a heart disease which he had before the accident