What causes some radionuclides to emit beta particles?
Beta minus particle (β-) emission occurs when the ratio of neutrons to protons in the nucleus is too high. An excess neutron transforms into a proton and an electron. The proton stays in the nucleus and the electron is ejected energetically. This process decreases the number of neutrons by one and increases the number of protons by one. Since the number of protons in the nucleus of an atom determines the element, the conversion of a neutron to a proton actually changes the radionuclide to a different element. Often, gamma ray emission accompanies the emission of a beta particle. When the beta particle ejection doesn’t rid the nucleus of the extra energy, the nucleus releases the remaining excess energy in the form of a gamma photon. The decay of technetium-99, which has too many neutrons to be stable, is an example of beta decay. A neutron in the nucleus converts to a proton and a beta particle. The nucleus ejects the beta particle and some gamma radiation. The new atom retains the sam
