Beta minus decay

β− decay is the decay of an element down the periodic table. It occurs when an element brings with it one too many neutrons and the element becomes unstable. What happens next is the element converts the extra neutron into a proton and releases an electron and a antineutrino. The result is that the element gets downgraded into the element that came before it. For example Carbon 10 (C₁₀) brings one too many neutrons and decays into Boron 10 (B_10).