polonium (puh-LOH-nee-uhm) n. Symbol "Po." ... It has 27 isotopes ranging in mass number from 192 to 218, of which Po 210, with a half-life of 138.39 days, is the most readily available.

When a radioactive atom emits an alpha particle the mass number decreases by four and the atomic number drops by two. Here is the equation for the alpha decay of radon-219 into polonium.

There are around 30 different isotopes of polonium ranging in atomic mass from 194 to 218, only differing from each other in their neutron number. The important one is polonium-210, which happens ...