12. **Electron Capture** - Explain the process of electron capture in radioactive decay. - Provide examples of elements undergoing electron capture?

Electron capture is a type of radioactive decay process in which an atom's nucleus absorbs an inner-shell electron, usually from the K or L shell, converting a proton into a neutron. This process results in the emission of a neutrino and a gamma ray.

During electron capture, the atom's atomic number decreases by one, while the mass number remains the same. This leads to the formation of a new element with a lower atomic number.

Examples of elements that undergo electron capture include:
1. Potassium-40 (40K) decays by electron capture to form Argon-40 (40Ar).
2. Calcium-40 (40Ca) decays by electron capture to form Argon-40 (40Ar).
3. Krypton-81 (81Kr) decays by electron capture to form Bromine-81 (81Br).

Electron capture is an important process in understanding the behavior of radioactive elements and their decay pathways.