Beta decay is a type of radioactive decay where the nucleus emits a beta particle, used in medical applications. It occurs when an atom is unstable due to excess neutrons or protons, converting them to stabilize the nucleus and transforming the atom into another element. Beta particles can be electrons or positrons, and have a greater penetrating power than alpha particles but less than gamma particles. They can be stopped with metal or paper, but can damage cells in the body if ingested.
Beta decay is a form of radioactive decay in which the nucleus of an atom undergoes a change that causes it to emit a beta particle. The other types of radioactive decay are alpha decay and gamma decay. Besides being a topic of general scientific interest, beta decay has a number of practical applications, especially in medicine, where beta particles are sometimes used to shrink or kill tumors. Beta decay can also be used in medical imaging studies as a tracer.
Atoms undergo beta decay when they are unstable because they have too many neutrons or too many protons. To stabilize itself, the excess neutrons or protons are converted, conserving mass and making the nucleus more stable. In the process, the atom also transforms into another element, because while the overall number of particles in the nucleus stays the same, the balance of protons and neutrons changes.
In beta minus decay, an excess neutron becomes a proton and the nucleus emits an electron and an antineutrino. The electron is the beta particle, while
the antineutrino is a particle with some unusual properties. The existence of neutrinos and antineutrinos was hypothesized as early as the 1930s, but it wasn’t until the 1950s that researchers were able to prove the existence of such particles. Three neutrino flavors have been identified, along with their corresponding antineutrinos. (And yes, “flavor” is a technical term in the vast world of particle physics.)
When a nucleus undergoes beta plus decay, a proton is converted to a neutron, with the nucleus emitting a positron and a neutrino. Beta particles can be electrons or positrons, as illustrated, depending on whether a nucleus goes through beta minus or beta plus decay. Before researchers realized that beta particles were just electrons or positrons, they referred to these particles as “beta rays,” which is why some antiquated texts contain references to beta rays.
A beta particle has a greater penetrating power than an alpha particle, but less than a gamma particle. Beta particles can be stopped with a thick sheet of metal, a large air pocket, or several sheets of paper. This makes them relatively safe to bypass, as long as safety precautions are observed when people are around elements that undergo beta decay.
Like alpha particles, however, beta particles can wreak havoc if they enter the body. Sometimes, this trait is used to advantage, such as when radioactive elements are introduced into the body to treat cancer. In cases where beta particles aren’t introduced on purpose, however, they can damage cells in the body or even cause reproductive health problems by interfering with egg and sperm cells.
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