Electron Capture in Nucleus

Electron capture is a nuclear decay process that occurs in some unstable atomic nuclei where an orbiting electron is captured by the nucleus; this results in a transformation of a proton into a neutron.

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• In an atom, protons and neutrons are held together in the nucleus by the strong nuclear force. 
  
• However, in certain nuclei, the number of protons is large enough that the electrostatic force between them starts to outweigh the attractive nuclear force, causing the nucleus to become unstable.
  

During electron capture, one of the inner shell electrons of the atom is captured by the nucleus. 

• This can only occur if there is a vacancy in one of the lower energy levels of the nucleus. 
  
• As a result, a proton is converted into a neutron, and a neutrino is emitted to conserve energy and momentum.
  

The equation for electron capture can be represented as follows:

Z (atomic number) + e− (electron) → Z−1 (atomic number decreases by 1) + ν (neutrino)

• The resulting nucleus has one less proton than before but the same mass number, as a neutron takes the place of the lost proton. 
  
• This changes the identity of the atom, as the atomic number determines the element, but it does not significantly affect the atomic mass.
  

Electron capture is commonly observed in large atomic nuclei with a high proton-to-neutron ratio, typically found in elements with high atomic numbers, such as iodine or tungsten. This process has implications in nuclear chemistry, astrophysics, and medical imaging techniques, as it is used in positron emission tomography (PET) scans.