Identify the parent nuclide and write the complete decay equation in the $^\textrm{A}\textrm{Z}\textrm{X}\textrm{N}$notation:$\alpha$decayproducing$^{208}\textrm{Pb}$.Theparentnuclideisinthedecayseriesproducedby$^{232}\textrm{Th}$, the only naturally occurring isotope of thorium.

Video Transcript

This is College Physics Answers with Shaun Dychko. α decay produces lead-208 so α decay produces an α particle, which is a helium nucleus— it has 2 protons and 2 neutrons for a total of 4 nucleons— and lead-208 has an atomic number of 82 which we can figure out from this appendix A here lead-208 has an atomic number of 82 so that means there are 82 protons, which leaves 126 neutrons left over when you subtract 82 from 208 total nucleons. So the α decay is the result of this parent nuclide shedding 2 protons and 2 neutrons in the form of this helium nucleus leaving behind this daughter nuclide that has 2 fewer protons 2 fewer neutrons than the parent nuclide. So that means there must have been 84 protons in the parent nuclide and 128 neutrons for a total of 212 nucleons and the element with an atomic number of 84 is polonium with a symbol 'Po'. There we go!