In beta decay, what is emitted from the nucleus?

In beta decay, the nucleus emits an electron or a positron as a result of a transformation within the atom. This process occurs when a neutron is converted into a proton, which releases an electron known as a beta particle. Conversely, in the case of positron emission, a proton is transformed into a neutron, releasing a positron as a result. This is fundamental to the concept of beta decay, which is one of the primary types of radioactive decay. The emitted particles change the atomic number of the element, leading to the formation of a new element in the decay process.

The other options—photon, neutron, and alpha particle—do not describe the emissions associated with beta decay. A photon is related to electromagnetic radiation rather than particle emission, neutrons are involved in certain decay processes but not specific to beta decay, and alpha particles, which consist of two protons and two neutrons, are emitted during alpha decay rather than beta decay.