Elemental samples in a mass spectrometer form mostly +1 ions. Under this condition, each peak's m/z value directly reports which quantity?

Core Concept

With z = +1, the mass-to-charge ratio reduces to the ion's mass itself. Each peak therefore lines up with a single isotope's mass number, which is how spectra reveal isotopic makeup. Doubly charged ions would shift the same isotope to a lower apparent m/z, so the +1 assumption keeps positions equal to masses.