Question 4.5: Magnesium is a macromineral needed in the contraction of mus......
Magnesium is a macromineral needed in the contraction of muscles and metabolic reactions. Using Table 4.7, calculate the atomic mass for magnesium using the weighted average mass method.
| TABLE 4.7 Isotopes of Magnesium | |||
| Atomic Symbol | ^{24}_{12}Mg | ^{25}_{12}Mg | ^{26}_{12}Mg |
| Name | Mg-24 | Mg-25 | Mg-26 |
| Number of Protons | 12 | 12 | 12 |
| Number of Electrons | 12 | 12 | 12 |
| Mass Number | 24 | 25 | 26 |
| Number of Neutrons | 12 | 13 | 14 |
| Mass of Isotope (amu) | 23.99 | 24.99 | 25.98 |
| Percent Abundance | 78.70 | 10.13 | 11.17 |
Step-by-Step
Table 1
STEP 1 Multiply the mass of each isotope by its percent abundance divided by 100.
Table 2
STEP 2 Add the contribution of each isotope to obtain the atomic mass.
Atomic mass of Mg = 18.88 amu + 2.531 amu + 2.902 amu
\space = 24.31 amu (weighted average mass)
Table 1
| ANALYZE THE PROBLEM | Given | Need | Connect |
| percent abundance, atomic mass |
atomic mass of Mg | weighted average mass |
Table 2
| Atomic Symbol | Mass (amu) | Percent Abundance | Contribution to the Atomic Mass |
| ^{24}_{12}Mg | 23.99 × | \frac{78.70}{100} = | 18.88 amu |
| ^{25}_{12}Mg | 24.99 × | \frac{10.13}{100} = | 2.531 amu |
| ^{26}_{12}Mg | 25.98 × | \frac{11.17}{100} = | 2.902 amu |
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