The nucleus shown undergoes beta-minus decay. How many protons will the nucleus have after it decays?
131/53 I
a) 54
b) 130
c) 52
d) 132
In beta-minus decay, a neutron is converted into a proton, emitting an electron and an antineutrino. This means the atomic number (number of protons) will increase by one, while the mass number (number of protons and neutrons) stays the same.
So in this case, the nucleus starts with 53 protons (since the atomic number is 53) and after beta-minus decay it will have 54 protons.
Therefore, the answer is (a) 54.