7440-35-9 Usage
Description
Americium is a synthetic radioactive element of atomic number 95, a member of the actinide series, and a radioactive metallic transuranic element belonging to the actinoids. It is not found naturally on Earth but is synthesized from plutonium. Americium is a highly toxic, silvery metal with two forms: α-Am, which is hexagonal, and β-Am, which is cubic. It has a melting point of 1,176°C, a boiling point of 2,607°C, and a density of 13.68 g/cm3. The most stable isotope of americium is 243Am, with a half-life of 7.37 × 103 years.
Uses
Used in Gamma Radiography:
Americium is used as a gamma ray source for radiography, particularly in portable X-ray instruments that can be easily transported for emergency use. The high-energy gamma rays emitted by americium-241 are useful for this application.
Used in Radiochemical Research:
Americium is utilized in radiochemical research due to its radioactive properties and the various isotopes it possesses.
Used as a Diagnostic Aid:
Americium-241 is used as a diagnostic aid to check the quality of welds in metals, taking advantage of its gamma ray emissions.
Used in Electronic Devices:
Americium is employed in the manufacturing of electronic devices, specifically in household smoke alarms. The americium-141 isotope emits alpha particles that ionize air, improving its electrical conductivity. Smoke reduces this conductivity, thus triggering the alarm.
Used in the Production of Americium-241:
Americium-241 is produced by bombarding plutonium-239 with high-energy neutrons, resulting in the isotope plutonium-240, which is then bombarded with neutrons to form plutonium-241. This isotope eventually decays into americium-241 through the process of beta decay.
Used in Thyroid Disorder Diagnosis:
Americium has been used to diagnose thyroid disorders, as mentioned in the chemical properties section.
Isotopes
There are 24 isotopes of americium. All are radioactive with half-lives rangingfrom 72 microseconds to over 7,000 years. Five of americium’s isotopes are fissionablewith spontaneous alpha decay.
Origin of Name
Named after the continent America because Europium was named
after the European continent.
Characteristics
Although americium’s main valence (oxidation state) is +3, it is tetravalent. It can formcompounds with its ions of +4, +5, and +6, particularly when oxidized. Its most stable isotopeis americium-243, with a half-life of 7,379 years, which, over time through alpha decay,transmutates into neptunium-239.
History
Americium was the fourth transuranium element to be
discovered; the isotope 241 Am was identified by Seaborg,
James, Morgan, and Ghiorso late in 1944 at the wartime
Metallurgical Laboratory of the University of Chicago as the
result of successive neutron capture reactions by plutonium
isotopes in a nuclear reactor:
239Pu(n,γ)→240Pu(n,γ)→241Pu?β →83Am
Since the isotope 241Am can be prepared in relatively pure form
by extraction as a decay product over a period of years from
strongly neutron-bombarded plutonium, 241Pu, this isotope is
used for much of the chemical investigation of this element.
Better suited is the isotope 243Am due to its longer half-life
(7.37 × 103 years as compared to 432.2 years for 241Am). A mixture
of the isotopes 241Am, 242Am, and 243Am can be prepared
by intense neutron irradiation of 241Am according to the reactions
241Am (n, γ) → 242Am (n, γ) → 243Am. Nearly isotopically
pure, 243Am can be prepared by a sequence of neutron
bombardments and chemical separations as follows: neutron
bombardment of 241Am yields 242Pu by the reactions 241Am (n,
γ) → 242Am → 242Pu, after chemical separation the 242Pu can
be transformed to 243Am via the reactions 242Pu (n, γ) → 243Pu
→ 243Am, and the 243Am can be chemically separated. Fairly
pure 242Pu can be prepared more simply by very intense neutron
irradiation of 239Pu as the result of successive neutroncapture
reactions. Seventeen radioactive isotopes and isomers
are now recognized. Americium metal has been prepared by
reducing the trifluoride with barium vapor at 1000 to 1200°C
or the dioxide by lanthanum metal. The luster of freshly prepared
americium metal is white and more silvery than plutonium
or neptunium prepared in the same manner. It appears
to be more malleable than uranium or neptunium and
tarnishes slowly in dry air at room temperature. Americium
is thought to exist in two forms: an alpha form which has a
double hexagonal close-packed structure and a loose-packed
cubic beta form. Americium must be handled with great care
to avoid personal contamination. As little as 0.03 μCi of 241Am
is the maximum permissible total body burden. The alpha activity
from 241Am is about three times that of radium. When
gram quantities of 241Am are handled, the intense gamma activity
makes exposure a serious problem. Americium dioxide,
AmO2, is the most important oxide. AmF3, AmF4, AmCl3,
AmBr3, AmI3, and other compounds have been prepared. The
isotope 241Am has been used as a portable source for gamma
radiography. It has also been used as a radioactive glass thickness
gage for the flat glass industry, and as a source of ionization
for smoke detectors. Americum-243 (99%) is available
from the Oak Ridge National Laboratory at a cost of about
$750/g plus packing charges.
Hazard
All the isotopes and compounds of americium are deadly sources of radiation and causeradiation poisoning and death. Precautions must be taken when working with it. The smallamount of americium-241 found in smoke detectors in household smoke alarms is harmlessunless the isotope is removed and swallowed.
Check Digit Verification of cas no
The CAS Registry Mumber 7440-35-9 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,4,4 and 0 respectively; the second part has 2 digits, 3 and 5 respectively.
Calculate Digit Verification of CAS Registry Number 7440-35:
(6*7)+(5*4)+(4*4)+(3*0)+(2*3)+(1*5)=89
89 % 10 = 9
So 7440-35-9 is a valid CAS Registry Number.
InChI:InChI=1/Am
