Definition of Beta Decay
Beta decay is a type of radioactive decay in which an unstable atomic nucleus spontaneously transforms into a different nucleus by emitting a beta particle. This process involves the weak nuclear force, one of the four fundamental forces of nature. During beta decay, either a neutron changes into a proton (beta-minus decay) or a proton changes into a neutron (beta-plus decay), resulting in a change in the element's identity.
Types of Beta Decay and Emitted Particles
There are two main types of beta decay: beta-minus (β⁻) decay and beta-plus (β⁺) decay. In beta-minus decay, a neutron converts into a proton, emitting an electron (β⁻ particle) and an antineutrino. In beta-plus decay, a proton converts into a neutron, emitting a positron (β⁺ particle, the antiparticle of an electron) and a neutrino. A third, less common type is electron capture, where an atomic electron is absorbed by the nucleus, converting a proton into a neutron and emitting a neutrino.
A Practical Example: Carbon-14 Dating
A classic example of beta-minus decay is the transformation of Carbon-14 (¹⁴C) into Nitrogen-14 (¹⁴N). An unstable carbon-14 nucleus, which has 6 protons and 8 neutrons, undergoes beta-minus decay. One of its neutrons transforms into a proton, emitting an electron and an antineutrino. The resulting nucleus now has 7 protons and 7 neutrons, making it stable Nitrogen-14. This specific decay is fundamental to carbon-14 dating, a method used to determine the age of organic materials.
Importance and Applications of Beta Decay
Beta decay plays a crucial role in various scientific and practical applications. Beyond radiometric dating (like carbon-14 dating), beta-emitting isotopes are widely used in medicine for diagnostic imaging (e.g., Positron Emission Tomography or PET scans, which utilize beta-plus emitters) and cancer therapy. In industry, they are used in thickness gauges, smoke detectors, and for sterilizing medical equipment and food. The understanding of beta decay is also fundamental to nuclear power generation and research in particle physics.