Carbon-40 is a highly unstable isotope, meaning it decays rapidly. It decays primarily through beta-minus decay.

Here's what happens:

* Beta-minus decay: A neutron inside the carbon-40 nucleus transforms into a proton, emitting an electron (beta particle) and an antineutrino. This process increases the atomic number by one while keeping the mass number the same.

Therefore, carbon-40 (C-40) decays into nitrogen-40 (N-40):

C-40 --> N-40 + e- + ν̅e

Nitrogen-40 is also unstable and decays further through beta-minus decay to oxygen-40:

N-40 --> O-40 + e- + ν̅e

However, it's important to note that the half-life of carbon-40 is extremely short (around 192 milliseconds). This means that it decays very quickly, so it's not something you'd encounter naturally.