If a pair of carbon atoms are fused, and the product were to emit a beta particle, ........?

Question

what element would be produced?

Answer 1

Assuming Carbon-12, you would end up with 12 protons and 12 neutrons, or Magnesium-24.

Beta decay works two ways: a neutron transmutes into a proton and an electron, or a proton into a neutron and an anti-electron. These would produce Aluminum-24 and Sodium-24, respectively.