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 == Mass-Energy equivalence == 

 So first and foremost, this section begins by making the statement: 
  ""By mass–energy equivalence, the electronvolt is also a unit of mass."" 
 though it is true that energy and mass can be converted between eachother, mass units and energy units are not the same thing. You can never write ""x electronvolts = y kilograms"", It just doesn't work that way. Saying that electronvolts are a UNIT of mass is always wrong, saying mass can be expressed in terms of energy and energy can be (sort of) expressed in terms of mass is significantly more correct. The current wordage could prove to be misleading to readers who don't understand what is actually meant to be said. 

 Now, I don't think this section even really belongs in an article on a unit of measure, since it is something which pertains to energy in general and the units used have next to no relevance on the matter. In other words, talking about this does not tell someone anything more about electronvolts. If the statement about electronvolts also being a unit of mass were true, then that would be another matter altogether, but since it doesn't, I believe this section doesn't really add anything to the article. 
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