Question

Because of the radioactive decay of uranium and thorium in rocks and soil, radium-228, a decay product of Thorium-232, can be found in drinking water. This isotope has a half-life of 5.75 years and an atomic number of 88. If Ra-228 undergoes beta decay, what would the atomic number of the new element be? What would the mass number of this isotope be? Explain your reasoning (e.g. Explain what happens during beta decay).

Answer 1

Answer: The atomic number and mass number of the new element formed is 89 and 228 respectively.

Explanation:

Beta decay is defined as the process in which beta particle is emitted. In this process, a neutron gets converted to a proton and an electron.  The released beta particle is also known as electron.

In this process, the atomic number of the daughter nuclei gets increased by a factor of 1 but the mass number remains the same.

$_Z^A\textrm{X}\rightarrow _{Z+1}^A\textrm{Y}+_{-1}^0\beta$

The chemical equation for the beta decay of Ra-228 follows:

$_{88}^{228}\tyextrm{Ra}\rightarrow _{89}^{228}\textrm{Ac}+_{-1}^0\beta$

Hence, the atomic number and mass number of the new element formed is 89 and 228 respectively.