For 10 points, give this number equal to the neutral pH value.
In mass spectrometry, an aromatic cation with this many carbon atoms often appears at m over z equals 91. The signal for the central proton of an isopropyl group will have this many peaks in proton NMR. A violet-colored strong oxidizing agent has a metal in this oxidation state. That compound is potassium permanganate. This is the number of elemental gases that are diatomic at standard conditions. This integer is equal to the negative log of hydronium concentration of pure water at 25 degrees Celsius, and is also the number of valence electrons possessed by the most electronegative element, fluorine. For 10 points, give this number equal to the neutral pH value.
In mass spectrometry, an aromatic cation with this many carbon atoms often appears at m over z equals 91.
seven [or +7]