Radioactive dating after 2 half lives
Gamma rays, which are unaffected by the electric field, must be uncharged. Because the loss of an α particle gives a daughter nuclide with a mass number four units smaller and an atomic number two units smaller than those of the parent nuclide, the daughter nuclide has a larger n:p ratio than the parent nuclide.
If the parent nuclide undergoing α decay lies below the band of stability (refer to Chapter 21.1 Nuclear Structure and Stability), the daughter nuclide will lie closer to the band.
Cobalt-60 emits γ radiation and is used in many applications including cancer treatment: Positron emission is observed for nuclides in which the n:p ratio is low. Positron decay is the conversion of a proton into a neutron with the emission of a positron.
The n:p ratio increases, and the daughter nuclide lies closer to the band of stability than did the parent nuclide.
Electron capture has the same effect on the nucleus as does positron emission: The atomic number is decreased by one and the mass number does not change.
This increases the n:p ratio, and the daughter nuclide lies closer to the band of stability than did the parent nuclide.
During the beginning of the twentieth century, many radioactive substances were discovered, the properties of radiation were investigated and quantified, and a solid understanding of radiation and nuclear decay was developed.
The spontaneous change of an unstable nuclide into another is radioactive decay.
Iodine-131 is an example of a nuclide that undergoes β decay: Beta decay, which can be thought of as the conversion of a neutron into a proton and a β particle, is observed in nuclides with a large n:p ratio.Ernest Rutherford’s experiments involving the interaction of radiation with a magnetic or electric field (Figure 2) helped him determine that one type of radiation consisted of positively charged and relatively massive α particles; a second type was made up of negatively charged and much less massive β particles; and a third was uncharged electromagnetic waves, γ rays.We now know that α particles are high-energy helium nuclei, β particles are high-energy electrons, and γ radiation compose high-energy electromagnetic radiation.Figure 3 summarizes these types of decay, along with their equations and changes in atomic and mass numbers.Positron emission tomography (PET) scans use radiation to diagnose and track health conditions and monitor medical treatments by revealing how parts of a patient’s body function (Figure 4).