To calculate the average atomic mass of strontium, we need to take into account both the masses and the abundances of its isotopes. Below is a step-by-step solution to find the average atomic mass:
1. Convert the Percent Abundances to Decimal Form:
- For \( \text{Sr-84} \):
[tex]\[ 0.56\% = 0.56 / 100 = 0.0056 \][/tex]
- For \( \text{Sr-86} \):
[tex]\[ 9.86\% = 9.86 / 100 = 0.0986 \][/tex]
- For \( \text{Sr-87} \):
[tex]\[ 7.00\% = 7.00 / 100 = 0.0700 \][/tex]
- For \( \text{Sr-88} \):
[tex]\[ 82.58\% = 82.58 / 100 = 0.8258 \][/tex]
2. Multiply the Mass of Each Isotope by Its Decimal Abundance:
- For \( \text{Sr-84} \):
[tex]\[ 83.913428 \times 0.0056 = 0.4704 \][/tex]
- For \( \text{Sr-86} \):
[tex]\[ 85.909273 \times 0.0986 = 8.4675 \][/tex]
- For \( \text{Sr-87} \):
[tex]\[ 86.908902 \times 0.0700 = 6.0836 \][/tex]
- For \( \text{Sr-88} \):
[tex]\[ 87.905625 \times 0.8258 = 72.5983 \][/tex]
3. Sum These Products to Find the Average Atomic Mass:
[tex]\[
\text{Average Atomic Mass} = 0.4704 + 8.4675 + 6.0836 + 72.5983 = 87.6198
\][/tex]
4. Round the Result to Two Decimal Places:
[tex]\[
\text{Average Atomic Mass} \approx 87.62 \, \text{amu}
\][/tex]
So, the average atomic mass of strontium is:
[tex]\[
\boxed{87.62} \, \text{amu}
\][/tex]
