If a radioisotope decays into an alpha particle and lead-208 what was the original element?

Answer 1

Since an alpha particle has 2 protons and 2 neutrons, you have to add 4 to the Atomic Mass. You also have to add 2 to the atomic number. That is, look up the number for protactinium in a periodic table, and add two to that number.

Answer 2

If we have lead-208 (Pb-208) resulting from an alpha decay then it must have come from pollonium-212 (Po-212). The balanced equation might look like this: 84212Po => 24He + 82208Pb Note that the subscripts and superscripts add up on both sides of the equation here. We see 84 = 2 + 82, and 212 = 4 + 208. All you need to remember is that the subscripts are the atomic numbers of the elements involved, and you can look those up on any Periodic Table. There is a link below to a related question, and also one to the Wikipedia periodic table of the elements. That bad boy is interactive! You can jet from one element to another with the click of a mouse! Worth checking out and bookmarking, fer sure.