Question

strontium consists of four isotopes with masses of 84 (abundance 0.50%) 86,( abundance of 9.9%), 87 (abundance of 7.0%) and 88 (abundance of 82.6%) calculate the atomic mass of strontium.

Answer 1

To calculate the atomic mass of strontium based on its isotopes and their respective abundances, we use the following formula:

\[
\text{Atomic Mass} = \sum (\text{mass of isotope} \times \text{fractional abundance})
\]

First, let's convert the percentages into fractions:

- For \(\text{Sr}^{84}\):
- Mass: 84
- Abundance: 0.50% = 0.0050

- For \(\text{Sr}^{86}\):
- Mass: 86
- Abundance: 9.9% = 0.099

- For \(\text{Sr}^{87}\):
- Mass: 87
- Abundance: 7.0% = 0.070

- For \(\text{Sr}^{88}\):
- Mass: 88
- Abundance: 82.6% = 0.826

Now we can calculate the contributions of each isotope to the atomic mass:

\[
\text{Contribution of } \text{Sr}^{84} = 84 \times 0.0050 = 0.42
\]
\[
\text{Contribution of } \text{Sr}^{86} = 86 \times 0.099 = 8.514
\]
\[
\text{Contribution of } \text{Sr}^{87} = 87 \times 0.070 = 6.09
\]
\[
\text{Contribution of } \text{Sr}^{88} = 88 \times 0.826 = 72.728
\]

Now sum all the contributions together:

\[
\text{Total Atomic Mass} = 0.42 + 8.514 + 6.09 + 72.728 = 87.752
\]

Therefore, the atomic mass of strontium (Sr) is approximately **87.75 u** (atomic mass units).