Chapter 2, Problem 3CT

Polonium is a rare element with 33 radioisotopes. The most common one, $\text{P}\text{o}$, has 84 protons and 126 neutrons. When $\text{P}\text{o}$ decays, it emits an alpha particle, which is a helium nucleus (2 protons and 2 neutrons). $\text{P}\text{o}$ decay is tricky to detect because alpha particles do not carry very much energy compared to other forms of radiation. For example, they can be stopped by a single sheet of paper or a few inches of air. That is one reason why authorities failed to discover toxic amounts of $\text{P}\text{o}$ in the body of former KGB agent Alexander Litvinenko until after he died suddenly and mysteriously in 2006. What element does an atom of $\text{P}\text{o}$ change into after it emits an alpha particle.