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Beta emission is a type of radioactive decay in which an unstable nucleus transforms to a more stable state. During this process, a neutron in the nucleus is converted into a proton and a beta particle—an electron—is released. For example, rubidium-90, with an atomic number of 37, emits a beta particle, resulting in a new atom, strontium-90, with an atomic number of 38. This is because the loss of a beta particle effectively increases the proton count by one. The balanced equation for this process is:
\( ^{90}_{37}Rb \rightarrow ^{90}_{38}Sr + ^0_{-1}\beta \).
Understanding this process is crucial for grasping various nuclear transformations and their implications in both natural and engineered systems.

Electron capture is a fascinating process where an atom's nucleus captures one of its own electrons and combines it with a proton, forming a neutron and a neutrino. This process decreases the atomic number by one but leaves the mass number unchanged. Taking selenium-72 as an example, it undergoes electron capture, turning into arsenic-72. The balanced nuclear equation reflects this subtle internal exchange:
\( ^{72}_{34}Se + ^0_{-1}e \rightarrow ^{72}_{33}As \).
This transformation is significant in many fields, including astrophysics and medical diagnostics, where electron capture is used in the imaging technique known as positron emission tomography (PET).

Positron emission is the mirror opposite of beta decay. Instead of an electron, a positron—which is an anti-electron—is emitted when a proton in the nucleus transforms into a neutron. The atom's atomic number goes down by one, while the mass number remains stable. In our textbook example, krypton-76 releases a positron and becomes bromine-76. The reaction is detailed as follows:
\( ^{76}_{36}Kr \rightarrow ^{76}_{35}Br + ^0_{+1}e \).
This concept is also integral to PET scans, where the emitted positrons encounter electrons, leading to annihilation and the release of gamma rays—key to imaging internal bodily functions.

Alpha radiation involves the ejection of an alpha particle, which is essentially a helium nucleus composed of two protons and two neutrons, from an unstable atom. Consequently, this type of emission reduces both the mass and atomic numbers — by four and two, respectively. Radium-226, for instance, undergoes alpha decay to become radon-222. The balanced equation for alpha decay of radium-226 is:
\( ^{226}_{88}Ra \rightarrow ^{222}_{86}Rn + ^4_2\alpha \).
Alpha particles, due to their relatively large mass, have a short range and can be stopped by a sheet of paper. However, if ingested or inhaled, they pose significant health risks due to their high ionization power.