[tex]\beta[/tex] - decay producing ${ }_{39}^{90} Y$
Answer (1)
β -decay increases the atomic number by 1 while the mass number remains the same.
The parent nucleus Z A X decays into 39 90 Y .
Therefore, A = 90 and Z = 39 − 1 = 38 .
The parent nucleus is 38 90 S r .
Explanation
Understanding the Problem We are given that a β -decay produces 39 90 Y . This means that some parent nucleus undergoes β -decay and transforms into Yttrium-90. Our goal is to identify this parent nucleus.
The Physics of Beta Decay In β − decay, a neutron within the nucleus converts into a proton, emitting an electron and an antineutrino. This process increases the atomic number (number of protons) by 1, while the mass number (total number of protons and neutrons) remains the same.
Determining Mass and Atomic Numbers Let's denote the parent nucleus as Z A X , where A is the mass number and Z is the atomic number. After the β -decay, this nucleus becomes 39 90 Y . This tells us that the mass number A of the parent nucleus must be 90, and its atomic number Z must be one less than that of Yttrium-90, since the atomic number increases by 1 during the decay.
Identifying the Parent Nucleus Therefore, the parent nucleus has a mass number A = 90 and an atomic number Z = 39 − 1 = 38 . The element with atomic number 38 is Strontium (Sr). Thus, the parent nucleus is 38 90 S r .
Examples
Beta decay is a type of radioactive decay where a proton is transformed into a neutron, or vice versa, inside an atomic nucleus. This process is crucial in various applications, such as carbon dating, where the decay of carbon-14 helps determine the age of ancient artifacts. In medicine, radioactive isotopes that undergo beta decay are used in imaging and cancer treatment. For instance, iodine-131, which decays by beta emission, is used to treat thyroid cancer. Understanding beta decay helps scientists and engineers harness these isotopes safely and effectively.
