Comment Re:Cosmic rays? (Score 1) 116
By 9.999998% pure, you mean that 9.999998% of your atoms are of the correct elements (Gallium and Arsenic). What element an atom is depends on its number of protons (which gives the charge of nucleus) - Ga has 31 and As has 33. Atoms of the same element may have different numbers of neutrons and hence different masses - these are known as different isotopes of the element. E.g. carbon (6 protons), can have 6 neutrons and a mass number of 12 or can have 8 neutrons and a number of 14. Different isotopes may be stable or decay at different rates. E.g. carbon 12 is stable, whereas carbon 14 decays with a half life of about 5000 years.
Seperating different elements is relatively straightforward (though getting anything 9.999998% pure probably ain't that easy) since they will have different chemical properties. Seperating different isotopes of the same element (e.g. to make uranium with mostly U235 which is the stuff you need for bombs) is more difficult since all you have to work with is the small difference in mass between the isotopes, so you might use a centifuge or some kind of diffusion based process.
Removing the radioactive isotopes from your lead to make non radioactive lead would need processes similar to those for producing weapons grade uranium, rather than producing pure GaAs (which will contain Ga and As atoms of a mixture of isotopes).
Seperating different elements is relatively straightforward (though getting anything 9.999998% pure probably ain't that easy) since they will have different chemical properties. Seperating different isotopes of the same element (e.g. to make uranium with mostly U235 which is the stuff you need for bombs) is more difficult since all you have to work with is the small difference in mass between the isotopes, so you might use a centifuge or some kind of diffusion based process.
Removing the radioactive isotopes from your lead to make non radioactive lead would need processes similar to those for producing weapons grade uranium, rather than producing pure GaAs (which will contain Ga and As atoms of a mixture of isotopes).
