Beta plus decay: mass balance?

[Chem.Stud.]

Hi:

I am taking a radiochemistry class, and I am confused by beta plus decay.

(1) p --> n + positron + electron-neutrino

The mass of a proton is less than the mass of a neutron. In addition, the neutrino has mass as does the positron.

(2) E = mc2

There must be come sort of balance, must there not? Mass cannot be created unless energy is consumed. So where does the nuclei get the energy from to convert a single proton into three different particles, one of which has a larger mass than the proton itself?

I hope I have made my confusion understandable. Also, my macbook would not let me use the greek characters or sub- and superscript.


Anders

 

[SteamKing]

The beta-plus decay cannot occur in a single proton due to the need for energy to be supplied from some external source.

See: http://en.wikipedia.org/wiki/Beta_decay

In heavier nuclei, beta-plus decay can occur if the original nucleus has a higher binding energy than the nucleus which remains after the emission of the beta-plus particle.

 

[Chem.Stud.]

Ahh, that makes sense. Thank you for your help.