How do you complete the following alpha decay reaction?

1 Answer
Jul 2, 2016

""_90^232 Th -> ""_88^228Ra + ""_2^4He23290Th22888Ra+42He

Explanation:

The general notation of a nuclide (XX) is:

""_Z^AXAZX

In wich ZZ is the number of protons and AA the mass number (protons + neutrons).

In alpha decay the nucleus emits a particle that contains 2 protons and 2 neutrons, which is similar to the nucleus of helium. So a notation for the nuclide (YY) that is left after emitting an alpha particle (""_2^4He42He) is:

""_(Z-2)^(A-4)Y + ""_2^4HeA4Z2Y+42He

Now you can complete the equation given in the example:

""_(88+2)^(228+4)X = ""_90^232X228+488+2X=23290X

The last step is finding the nuclide that has 90 protons and 142 neutrons in a table of nuclides. This appears to be Thorium (ThTh).

This makes the equation complete:

""_90^232 Th -> ""_88^228Ra + ""_2^4He23290Th22888Ra+42He