# Guessing decay modes

steph17
how can we guess the possible decay modes for an element with three given quantities: A, Z and mass difference in MeV

## Answers and Replies

Mentor
Mass difference to what?
You can check the masses of the nuclides that would be produced from the different decay modes, and see if such a decay is possible.

Gold Member
Mass difference to what?
I assume "mass difference" means "mass defect", i.e. the difference between the mass of the nucleus and its component nucleons (when unbound)

• steph17
Knowing A and Z and some logic will get you a very long way - the link below is a nuclear chart, coloured by decay mode. For example, a nucleus that is on the proton rich side of stability and of intermediate mass will decay in such a way that brings it closer to the valley of stability - a proton will have to turn into a neutron, so that element will probably decay via B+.

http://www.vanderbilt.edu/AnS/physi...cture_materials/wkb/audi_2003_decay_modes.png

• steph17
steph17
Mass difference to what?
You can check the masses of the nuclides that would be produced from the different decay modes, and see if such a decay is possible.
i was taught too the equation of mass difference of calculating the difference between the initial and final masses of the nuclides, but in the question that i was given only one element was mentioned, i got confused over there. for eg mass difference of hydrogen(A=1,Z=1)= 7.289 MeV, mass difference of Nb(A=92, Z=41)= -86.448 MeV, mass difference of Rb(A=92, Z=37)=-75.12MeV

Or can we just ignore the mass difference data and calculate the neutron-proton ratio and compare it to the valley of stability?

Mentor
i was taught too the equation of mass difference of calculating the difference between the initial and final masses of the nuclides, but in the question that i was given only one element was mentioned, i got confused over there.
You can look it up, if necessary.
Or can we just ignore the mass difference data and calculate the neutron-proton ratio and compare it to the valley of stability?
To get a rough estimate, yes, but it won't work for every isotope.