Isotopes

[Little Bang]

This question is probably right down UncleAl's alley. Does anyone know the how and the why of isotopes?

[UncleAl]

  Little Bang said:

This question is probably right down UncleAl's alley. Does anyone know the how and the why of isotopes?

Isotopes are nuclides with the same Z and different A,

 

http://en.wikipedia.org/wiki/Isotope

http://t2.lanl.gov/data/astro/molnix96/massd.html

 

Isotopes are not to be confused with nuclear isomers that have identical Z and A,

 

http://en.wikipedia.org/wiki/Nuclear_isomer

 

or with nuclear isotones or isobars.

[Qfwfq]

The why, in simple terms, is that for a given number Z of protons, the nucleus will be stable or at least metastable, if it has not too few and not too many neutrons. In some cases there is more than one fairly stable isotope. For a given Z the atoms are the same chemical element with just different mass.

 

The details of how stable a nucleus with a given Z and A will be, are complicated but can be worked out with quantum mechanics.