Polonium, element number 84, made the news in recent years when it was used in the assassination of a former KGB officer. It should be no surprise to learn, then, that polonium, besides being radioactive, is highly toxic in its own right. Partially because of that fact, and partially because any sizable amount of it would throw of enough radiation to kill you in short order, polonium is normally encountered in very small amounts when outside of a research laboratory, as is the case with my sample of polonium.
This sample is a .1μCi sample of Pb-210, a radioactive isotope of lead, mounted on the end of a needle. This source is meant to be used as a radiation source in a cloud chamber, which is exactly what I used it for. “But,” you may ask, “what is a sample of lead doing on the page for polonium?” The answer lies in the decay chain for Pb-210. It turns out that, in my collection, polonium is one of the elements which is be accounted for through radioactive decay chains. In this case, Pb-210 decays via emission of a beta particle into Bi-210, a radioactive isotope of bismuth. The Bi-210 then beta-decays into Po-210, which is how I can pass off a sample of lead as a sample of something much more exotic and expensive.