Electron Capture

When an atom undergoes electron capture, the atomic number Z decreases by one since Z represents the number of protons. However, the mass number A, which represents the total number of protons and electrons, remains the same. In other words, the overall mass in the nucleus remains constant.

The general equation for electron capture can be written as:

 \[  _{Z}^{A}\text{X} + e^{-} \rightarrow\ _{Z-1}^{A}\text{Y} + \nu_e \]​

Where:

– \( _{Z}^{A}\text{X} \) represents the parent nucleus

– e^– is the captured electron

– \( _{Z-1}^{A}\text{Y} \) is the daughter nucleus

– ν_e​ is the neutrino emitted during the process

1. Beryllium-7 captures an electron, converting one proton into a neutron, and transforms into Lithium-7, with the emission of a neutrino.

 \[ _{4}^{7}\text{Be} + e^{-} \rightarrow _{3}^{7}\text{Li} + \nu_e \]​

2. Krypton-81 captures an electron, causing a proton to convert into a neutron, which results in Bromine-81 and the emission of a neutrino.

\[ _{36}^{81}\text{Kr} + e^{-} \rightarrow _{35}^{81}\text{Br} + \nu_e \]

• Medical Imaging: Used in positron emission tomography (PET) scans, where electron capture isotopes are employed for detecting metabolic activity in tissues.
• Astrophysics: Plays a role in stellar processes, particularly in the formation of neutron stars, where electron capture reduces proton-rich elements.
• Environmental Dating: Krypton-81 electron capture is used in groundwater and ice core dating, helping scientists estimate the age of ancient water reserves.