The atomic mass of boron is found by calculating the weighted average of the masses of its isotopes, considering their relative abundances.
Understanding Boron Isotopes
Boron has two naturally occurring isotopes: Boron-10 (¹⁰B) and Boron-11 (¹¹B). Their masses are approximately 10.0 u and 11.0 u respectively (u represents atomic mass units). The relative abundance of each isotope is crucial in determining the average atomic mass.
Calculating the Atomic Mass
The calculation involves multiplying the mass of each isotope by its relative abundance (expressed as a decimal), and then summing the results. For Boron, the calculation is as follows:
- Boron-10: Abundance: 19.9% or 0.199. Mass contribution: 0.199 × 10.0 u = 1.99 u
- Boron-11: Abundance: 80.1% or 0.801. Mass contribution: 0.801 × 11.0 u = 8.811 u
Total Atomic Mass: 1.99 u + 8.811 u = 10.801 u
Therefore, the atomic mass of boron is approximately 10.8 u. This value is consistent with the value found on the periodic table. Minor discrepancies might arise due to rounding of isotopic masses and abundances. Several sources corroborate this method and result (LibreTexts, Chemistry LibreTexts, Study.com).
Key Considerations:
- Abundances: Accurate isotopic abundances are critical for an accurate atomic mass calculation. These abundances may vary slightly depending on the source.
- Units: Atomic mass units (u) are commonly used in these calculations.
- Weighted Average: The calculation is a weighted average, giving more weight to the more abundant isotope.
