The average atomic mass of silicon is given as 28.086 amu, and this value provides important insights into the relative abundances of its isotopes, which are silicon-28 (mass number 28), silicon-29 (mass number 29), and silicon-30 (mass number 30).
Since the average atomic mass is closer to 28 than to 29 or 30, we can infer that silicon-28 is the most abundant isotope. This is because the average atomic mass is a weighted average of the isotopic masses, meaning that isotopes with higher abundance have a larger impact on the average than those that are less abundant.
To quantify this, let’s consider the contributions of the isotopes. If silicon-28 were the only isotope present, the average would be exactly 28. If silicon-29 and silicon-30 were present in significant amounts, the average would shift closer to those values. Since the average is only slightly above 28, we can deduce that silicon-29 and silicon-30 must be present in relatively low abundances compared to silicon-28.
In summary, the average atomic mass of 28.086 amu suggests that silicon-28 is the dominant isotope in nature, while silicon-29 and silicon-30 are present in much lesser quantities.