Actinium
|
|
| |||||||||||||||||||||||||||||||||||||||||||
| General | |||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Name, Symbol, Number | actinium, Ac, 89 | ||||||||||||||||||||||||||||||||||||||||||
| Chemical series | Actinides | ||||||||||||||||||||||||||||||||||||||||||
| Group, Period, Block | 3 , 7, f | ||||||||||||||||||||||||||||||||||||||||||
| Density, Hardness | 10070 kg/m3, n/a | ||||||||||||||||||||||||||||||||||||||||||
| Appearance | silvery | ||||||||||||||||||||||||||||||||||||||||||
| Atomic properties | |||||||||||||||||||||||||||||||||||||||||||
| Atomic weight | (227) u | ||||||||||||||||||||||||||||||||||||||||||
| Atomic radius (calc.) | 195 (n/a) pm | ||||||||||||||||||||||||||||||||||||||||||
| Covalent radius | n/a pm | ||||||||||||||||||||||||||||||||||||||||||
| van der Waals radius | n/a pm | ||||||||||||||||||||||||||||||||||||||||||
| Electron configuration | [Rn]6d17s2 | ||||||||||||||||||||||||||||||||||||||||||
| e- 's per energy level | 2, 8,18,32,18, 9, 2 | ||||||||||||||||||||||||||||||||||||||||||
| Oxidation states (Oxide) | 3 (neutral) | ||||||||||||||||||||||||||||||||||||||||||
| Crystal structure | face centered cubic | ||||||||||||||||||||||||||||||||||||||||||
| Physical properties | |||||||||||||||||||||||||||||||||||||||||||
| State of matter | solid (__) | ||||||||||||||||||||||||||||||||||||||||||
| Melting point | 1323 K (1050 ?C / 1922 ?F) | ||||||||||||||||||||||||||||||||||||||||||
| Boiling point | 3473 K (3200 ?C / 5792 ?F) | ||||||||||||||||||||||||||||||||||||||||||
| Molar volume | 22.55 ×10-6 m3/mol | ||||||||||||||||||||||||||||||||||||||||||
| Heat of vaporization | n/a kJ/mol | ||||||||||||||||||||||||||||||||||||||||||
| Heat of fusion | 62 kJ/mol | ||||||||||||||||||||||||||||||||||||||||||
| Vapor pressure | unknown Pa at 1323 K | ||||||||||||||||||||||||||||||||||||||||||
| Velocity of sound | unknown m/s at 293.15 K | ||||||||||||||||||||||||||||||||||||||||||
| Miscellaneous | |||||||||||||||||||||||||||||||||||||||||||
| Electronegativity | 1.1 (Pauling scale) | ||||||||||||||||||||||||||||||||||||||||||
| Specific heat capacity | unknown J/(kg*K) | ||||||||||||||||||||||||||||||||||||||||||
| Electrical conductivity | unknown 106/m ohm | ||||||||||||||||||||||||||||||||||||||||||
| Thermal conductivity | 12 W/(m*K) | ||||||||||||||||||||||||||||||||||||||||||
| 1st ionization potential | 499 kJ/mol | ||||||||||||||||||||||||||||||||||||||||||
| 2nd ionization potential | 1170 kJ/mol | ||||||||||||||||||||||||||||||||||||||||||
| 3rd ionization potential | unknown kJ/mol | ||||||||||||||||||||||||||||||||||||||||||
| 4th ionization potential | unknown kJ/mol | ||||||||||||||||||||||||||||||||||||||||||
| Most stable isotopes | |||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||
| SI units & STP are used except where noted. | |||||||||||||||||||||||||||||||||||||||||||
Actinium is a chemical element in the periodic table that has the symbol Ac and atomic number 89.
| Contents |
Notable characteristics
Actinium is a silvery radioactive metallic element. Due to its intense radioactivity, Actinium glows in the dark with an eerie blue light. It is found only in traces in uranium ores as 227-Ac, an α and β emitter with a half-life of 21.773 years. One ton of uranium ore contains about a tenth of a gram of actinium.
Applications
It is about 150 times as radioactive as radium, making it valuable as a neutron source. Otherwise it has no significant industrial applications.
Actinium-225 is used in medicine to produce Bi-213 in a reusable generator or can be used alone as an agent for radio-immunotherapy.
History
Actinium was discovered in 1899 by Andr魌ouis Debierne, a French chemist, who separated it from pitchblende. Friedrich Otto 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.
Occurrence
Actinium is found in trace amounts in uranium ore, but more commonly is made in milligram amounts by the neutron irradiation of 226-Ra in a nuclear reactor. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300?C.
Isotopes
Naturally occurring actinium is composed of 1 radioactive isotope; 227Ac. 36 radioisotopes have been characterized with the most stable being 227-Ac with a half-life of 21.772 y, 225-Ac with a half-life of 10.0 days, and 226-Ac with a half-life of 29.37 h. 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 is217Ac which decays through alpha decay and electron capture. It has a half-life of 69 ns. Actinium also has 2 meta states.
Purified actinium-227 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 (206actinium) to 236 amu (236Ac).
Precautions
Actinium-227 is extremely radioactive, and in terms of its potential for radiation induced health effects, actinium-227 is about as dangerous as plutonium. Ingesting even small amounts of actinium-227 would represent a serious health hazard.
References
- Los Alamos National Laboratory - Actinium (http://periodic.lanl.gov/elements/89.html)
External links
- WebElements.com - Actinium (http://www.webelements.com/webelements/elements/text/Ac/index.html)
- EnvironmentalChemistry.com - Actinium (http://environmentalchemistry.com/yogi/periodic/Ac.html)