where formula_1 is the gyromagnetic ratio, "g" is a dimensionless number, called the g-factor, "q" is the charge, and "m" is the mass. The "g"-factor depends on the particle: it is for the electron, for the proton, and for the neutron. The proton and neutron are composed of quarks, which have a non-zero charge and a spin of , and this must be taken into account when calculating their g-factors. Even though the neutron has a charge , its quarks give it a magnetic moment. The proton and electron's spin magnetic moments can be calculated by setting and , respectively, where "e" is the elementary charge unit.