Expressed in terms of quark content, these would become: By convention, the flavor quantum numbers (strangeness, charm, bottomness, and topness) carry the same sign as the electric charge of the particle.
So, since the strange and bottom quarks have a negative charge, they have flavor quantum numbers equal to −1.
And since the charm and top quarks have positive electric charge, their flavor quantum numbers are +1.
From a quantum chromodynamics point of view, the Gell-Mann–Nishijima formula and its generalized version can be derived using an approximate SU(3) flavour symmetry because the charges can be defined using the corresponding conserved Noether currents.
In 1961 Glashow proposed a relation similar formula would also apply to the weak interaction:[4][5]: 152