Radiometric Dating

Isotopes and Radiometric Dating of Rocks

• An isotope is an element with different number of neutrons than protons

  • Unstable and decays over time into other elements ⇒ radioactive decay

• Exponential decay you can measure ⇒ half-life

  • Radiometric dating ⇒ determine age of rock by back-calculating to original amount

• Carbon has 3 isotopes ⇒

  • 12C has 6 protons, 6 neutrons; 13C has 6 protons, 7 neutrons; 14C has 6 protons, 8 neutrons
  • 14C decays over time to 14N

• 14C Half-life = ~5700 years
• Only date things ~50,000 years old

→ Ion