Hi: broadly, if the chord had F instead of F#, such an F would be at odds with E: the interval between E and F, that is either E-F or F-E is a MINOR 2nd interval (that is, a SEMITONE), which is highly dissonant, in contrast with E-F#, a MAJOR 2nd interval, which, though technically is a dissonance, is far less dissonant than the former. Greetings