Introduction to Geochemistry

Nucleosynthesis
! Solar (cosmic) abundances of the elements
• H and He are most abundant elements (primordial H, some He)
• First 50 elements show exponentially decreasing abundances
• After first 50 elements, abundances are very low
• Even-number nuclides are more abundant than odd-numbered nuclides
• Oddo-Harkins rule, a result of nuclear “magic numbers”
• Li, Be and B are very low in abundance
• nuclei are destroyed in stars or are weakly stable
• Fe is of anomalously high abundance
• 56 Fe is the most stable of all possible nuclear configurations
• Tc and Pm do not occur naturally in our solar system
• Z > 83 (Bi) have no stable isotopes
• Once thought Bi 209 was heaviest stable, but in 2002 was shown to have a
half-life of 1.9 x 10 19 years…