Beta particles are high-energy, high-speed electrons or positrons emitted from a radioactive nucleus during beta decay. They have a charge of either -1 (electron) or +1 (positron) and can penetrate materials more effectively than alpha particles.
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Beta decay occurs when a neutron in an unstable nucleus is converted into a proton, emitting a beta particle and an antineutrino.
There are two types of beta decay: beta-minus (β⁻) decay, which emits an electron, and beta-plus (β⁺) decay, which emits a positron.
Beta particles have greater penetrating power than alpha particles but less than gamma rays. They can pass through paper but are generally stopped by plastic or thin metal sheets.
The energy spectrum of beta particles is continuous because the energy is shared between the emitted beta particle and an accompanying neutrino.
In nuclear equations, beta-minus decay increases the atomic number by one while keeping the mass number constant.
Review Questions
What type of particle is emitted during beta-minus decay?
How do the atomic number and mass number change during beta-plus decay?
Why do beta particles have a continuous energy spectrum?
Gamma rays are high-energy electromagnetic waves emitted from a nucleus as it changes from an excited state to a ground energy state. They have high penetration power.