section_path: Characteristics/Isotopes
section_name: Isotopes
paragraph_text: Isotopes
  
  Naturally occurring silver is composed of two stable isotopes, Ag and Ag, with Ag being slightly more abundant (51.839% natural abundance). This almost equal abundance is rare in the periodic table. The atomic weight is 107.8682(2) u; this value is very important because of the importance of silver compounds, particularly halides, in gravimetric analysis. Both isotopes of silver are produced in stars via the s-process (slow neutron capture), as well as in supernovas via the r-process (rapid neutron capture).
  
  Twenty-eight radioisotopes have been characterized, the most stable being Ag with a half-life of 41.29 days, Ag with a half-life of 7.45 days, and Ag with a half-life of 3.13 hours. Silver has numerous nuclear isomers, the most stable being Ag (t = 418 years), Ag (t = 249.79 days) and Ag (t = 8.28 days). All of the remaining radioactive isotopes have half-lives of less than an hour, and the majority of these have half-lives of less than three minutes.
  
  Isotopes of silver range in relative atomic mass from 92.950 u (Ag) to 129.950 u (Ag); the primary decay mode before the most abundant stable isotope, Ag, is electron capture and the primary mode after is beta decay. The primary decay products before Ag are palladium (element 46) isotopes, and the primary products after are cadmium (element 48) isotopes.
  
  The palladium isotope Pd decays by beta emission to Ag with a half-life of 6.5 million years. Iron meteorites are the only objects with a high-enough palladium-to-silver ratio to yield measurable variations in Ag abundance. Radiogenic Ag was first discovered in the Santa Clara meteorite in 1978. Pd– Ag correlations observed in bodies that have clearly been melted since the accretion of the Solar System must reflect the presence of unstable nuclides in the early Solar System.