Charge here is just one thing that has to be conserved. Baryon number is a property of quarks and must also be conserved, and this prevents a neutron turning into an anti neutron as that would have opposite baryon number.
There are others such as isospin, lepton number…
These types of conservation laws are what limits the possible particle interactions.
There are others such as isospin, lepton number…
These types of conservation laws are what limits the possible particle interactions.