The relative isotopic mass of an isotope is calculated by taking into account the mass of each individual particle within the isotope and considering their respective abundances.
For boron-11 (abbreviated as ^11B), the relative isotopic mass is calculated as follows:
Relative Isotopic Mass = (Mass of isotope 1 × Abundance of isotope 1) + (Mass of isotope 2 × Abundance of isotope 2) + ...
In the case of boron, there are two isotopes: boron-10 (^10B) and boron-11 (^11B). The masses and abundances of these isotopes are:
^10B: Mass = 10.0129 atomic mass units (AMU) Abundance = 19.9% (0.199)
^11B: Mass = 11.0093 AMU Abundance = 80.1% (0.801)
To calculate the relative isotopic mass of boron-11:
Relative Isotopic Mass = (10.0129 AMU × 0.199) + (11.0093 AMU × 0.801)
Relative Isotopic Mass = 1.99386 AMU + 8.80702 AMU
Relative Isotopic Mass ≈ 10.80088 AMU
Therefore, the relative isotopic mass of boron-11 is approximately 10.80088 atomic mass units.