Electron Capture
Electron capture is a type of radioactive decay that happens inside an atom’s nucleus when one of its inner electrons is pulled in and combined with a proton. When this happens, the proton turns into a neutron, and a tiny particle called a neutrino is released. Since the number of protons in the nucleus decreases by one, the element itself changes into a different one. However, the overall mass of the atom stays the same. Electron capture usually happens in atoms that have too many protons and cannot release energy by other means.
Equation
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
– νe is the neutrino emitted during the process
Examples
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.
\[ _{36}^{81}\text{Kr} + e^{-} \rightarrow _{35}^{81}\text{Br} + \nu_e \]
Applications
- 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.
FAQs
Ans. The nucleus absorbs an electron from the atom’s electron cloud in electron capture. The nucleus emits a beta particle (either an electron or a positron) from itself during beta decay.
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References
Article was last reviewed on Monday, September 9, 2024