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Science / Periodic Table of Elements / Actinium (Ac): Atomic number: 89, Atomic mass: 227 g.mol -1, Electronegativity: 1.1, Density: 10.07 g.cm-3 at 20°C, Melting point: 1050 °C, Boiling point: 3250 °C, Vanderwaals radius: unknown, Ionic radius: unknown, Isotopes: 4, Electronic shell: [ Rn ] 6d1 7s2, Energy of first ionization: 664.6 kJ.mol -1, Energy of second ionization: 1165.5 kJ.mol -1, Discovered by: André Debierne in 1899. Actinium is a silvery radioactive metallic element. Actinium glows in the dark due to its intense radioactivity with a blue light. Actinium was discovered in 1899 by André-Louis 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. 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. Actinium in the environment It is found only in traces in uranium ores as 227-Ac, an a and ß 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 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-degrees C. Naturally occurring actinium is composed of 1 radioactive isotope; with 227-Ac being the most abundant (100% natural abundance). 27 radioisotopes have been characterized with the most stable being 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-life's that are less than 10 hours and the majority of these have half life's that are less than 1 minute. This element 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 (206-actinium) to 234 amu (234-actinium).
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Science / Periodic Table of Elements / Protactinium (Pa): Atomic number: 91, Atomic mass: 231.0359 g.mol -1, Electronegativity: 1.5, Density: 15.37 g.cm-3 at 20°C, Melting point: 1600 °C, Boiling point: unknown, Vanderwaals radius: unknown, Ionic radius: u MORE
Technology / Computers / Alternating Current (AC): Electricity running from the wall outlet. 120 Volts at 60Hz through a fuse or circuit breaker that can typically handle around 15-20 Amps. MORE