Which of the following is NOT a decay product of radon?

The correct choice is Bismuth-212, as it is not a decay product of radon. Radon decays through a series of steps, known as the decay chain. The most common isotope of radon, radon-222, undergoes a decay process that eventually leads to the formation of several different elements including polonium-218, lead-214, and polonium-214.

During this decay chain, radon-222 decays into polonium-218, which then decays into lead-214. The decay of lead-214 results in the formation of polonium-214. In contrast, bismuth-212 is part of a different decay series that originates from thorium-232 instead of radon. Understanding these decay chains is crucial for anyone assessing radon levels, as each product has different properties and implications for health and safety.