Big bang - put bigger thing into smaller container?

Actually, I made a mistake there. It's a neutron that produces a proton, an electron and an antineutrino (beta-minus decay). Net charge is conserved in the process.

In terms of quarks, the initial neutron and the final proton each contain 3 quarks. Neither of them contains any electrons or neutrinos. In the process, one of the quarks changes "flavor" from down to up.