# Guessing decay modes

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

mfb
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.

dukwon
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
e.bar.goum
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
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?

mfb
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.