Calculate average atomic mass from isotope abundances and masses
Atoms of the same element with different numbers of neutrons, resulting in different atomic masses.
The percentage of each isotope found naturally on Earth, determined by mass spectrometry.
The weighted average of all isotope masses, based on their natural abundances.
Average Atomic Mass = Σ (Isotope Mass × Fractional Abundance)
Where fractional abundance = percentage / 100
Carbon:
• C-12: 98.89% abundance, 12.000 amu
• C-13: 1.11% abundance, 13.003 amu
Calculation:
(12.000 × 0.9889) + (13.003 × 0.0111) = 12.01 amu