Atomic Number: 89
Atomic Weight: 227.000000
Family: Rare Earth Elements
CAS RN: 7440-34-8
Description: Silvery-white radioactive metal that glows in the dark.
State (25°C): Solid
Oxidation states: +3
Molar Volume: 22.54 cm3/mole
Valence Electrons: 6d17s2
|Boiling Point: 3473°K, 3200°C, 5792°F
Melting Point: 1323°K, 1050°C, 1922°F
Electrons Energy Level: 2, 8, 18, 32, 18, 9, 2
Isotopes: 31 + None Stable
Heat of Vaporization: unknown
Heat of Fusion: 62 kJ/mol
Density: 10.07 g/cm3 @ 300°K
Specific Heat: 0.12 J/g°K
Atomic Radius: 1.88Å
Ionic Radius: 1.119Å
Electronegativity: 1.1 (Pauling); 1 (Allrod Rochow)
1s2 2s2p6 3s2p6d10 4s2p6d10f14 5s2p6d10 6s2p6d1 7s2
Actinium was discovered in 1899 by Andre-Louis Debierne, a French chemist, who separated it from pitchblende. Friedrich Oskar Giesel independently discovered actinium in 1902. The chemical behavior of actinium is similar to that of the rare earth lanthanum.
The word actinium comes from the Greek aktis, aktinos, meaning beam or ray.
Actinium is a rare, extremely radioactive metal that glows in the dark. Eventual priority was given to Debierne's work.
Actinium is a silvery, radioactive, metallic element. Due to its intense radioactivity, Actinium glows in the dark with a pale blue light. It is found only in traces in uranium ores as 227Ac, an alpha and beta emitter with a half-life of 21.773 years. One ton of uranium ore contains about a tenth of a gram of actinium.
Actinium is found in trace amounts in uranium ore, but more commonly is made in milligram amounts by the neutron irradiation of 226Ra in a nuclear reactor. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300ºC.
It is about 150 times as radioactive as radium, making it valuable as a neutron source. Otherwise it has no significant industrial applications.
225Ac is used in medicine to produce 213Bi in a reusable generator or can be used alone as an agent for radio-immunotherapy for Targeted Alpha Therapy (TAT). 225Ac was first produced artifically by the ITU in Germany using a cyclotron and by Dr Graeme Melville at St George Hospital in Sydney using a linac in 2000.
Naturally occurring actinium is composed of 1 radioactive isotope; 227Ac. 36 radioisotopes have been characterized with the most stable being 227Ac with a half-life of 21.772 years, 225Ac with a half-life of 10.0 days, and 226Ac with a half-life of 29.37 hours. All of the remaining radioactive isotopes have half-lifes that are less than 10 hours and the majority of these have half lifes that are less than 1 minute. The shortest-lived isotope of actinium is 217Ac which decays through alpha decay and electron capture. It has a half-life of 69 ns. Actinium also has 2 meta states.
Purified 227Ac comes into equilibrium with its decay products at the end of 185 days, and then decays according to its 21.773-year half-life.
The isotopes of actinium range in atomic weight from 206 amu (206Ac) to 236 amu (236Ac).
Samples of actinium quickly decay to thorium and francium. The element is obtained as an impurity in pitchblende, an ore mined for its uranium content. One-tenth of one gram of actinium can be recovered from 1 ton of pitchblende.
|Ac235|| 40 seconds|
|Ac236|| 2 minutes|
|227Ac is extremely radioactive, and in terms of its potential for radiation induced health effects, 227Ac is even more dangerous than plutonium. Ingesting even small amounts of 227Ac would present a serious health hazard.|
|Ionization Energy (eV): 5.17 eV
Estimated Crustal Abundance: 5.5×10-10 milligrams per kilogram
Estimated Oceanic Abundance: unknown
(Gr. aktis, aktinos, beam or ray). Discovered by Andre Debierne in 1899 and independently by F. Giesel in 1902. Occurs naturally in association with uranium minerals. Actinium-227, a decay product of uranium-235, is a beta emitter with a 21.6-year half-life. Its principal decay products are thorium-227 (18.5-day half-life), radium-223 (11.4-day half-life), and a number of short-lived products including radon, bismuth, polonium, and lead isotopes. In equilibrium with its decay products, it is a powerful source of alpha rays. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300-degrees C. The chemical behavior of actinium is similar to that of the rare earths, particularly lanthanum. Purified actinium comes into equilibrium with its decay products at the end of 185 days, and then decays according to its 21.6-year half-life. It is about 150 times as active as radium, making it of value in the production of neutrons.
Source: CRC Handbook of Chemistry and Physics, 1913-1995. David R. Lide, Editor in Chief. Author: C.R. Hammond