Inductively coupled plasma mass spectrometry argon ions. Making the plasma from argon, instead of other gases, has several advantages. First, argon is abundant (in the atmosphere, as a result of the radioactive decay of potassium) and therefore cheaper than other noble gases. Argon also has a higher first ionization potential than all other elements except He, F, and Ne. Because of this high ionization energy, the reaction (Ar + e → Ar) is more energetically favorable than the reaction (M + e → M). This ensures that the sample remains ionized (as M) so that the mass spectrometer can detect it. Argon can be purchased
Noble gas compound they are less strongly attracted to the positively charged nucleus. This results in an ionization energy low enough to form stable compounds with the most electronegative elements, fluorine and oxygen, and even with less electronegative elements such as nitrogen and carbon under certain circumstances. When the family of noble gases was first identified at the end of the nineteenth century, none of them was observed to form any compounds and it was initially believed that they were all "inert gases" (as they were then known) which could not form compounds. With the development of atomic theory in the early twentieth