The average atomic mass of magnesium is 24.312 u.
Understanding Atomic Mass
What is Atomic Mass?
Atomic mass is the mass of an atom, typically expressed in atomic mass units (u). It represents the total mass of protons, neutrons, and electrons in an atom, or the average mass in a group of atoms. For a single atom, the contribution of electrons is very small.
Average Atomic Mass
The average atomic mass of an element is the weighted average of the atomic masses of its isotopes, based on their natural abundance.
Magnesium Isotopes and Their Contribution
Magnesium (Mg) has three stable isotopes that occur naturally. The isotopes and their properties are detailed below:
| Isotope | Mass (u) | Natural Abundance |
|---|---|---|
| $^{24}_{12}Mg$ | 23.98504 | Highest |
| $^{25}_{12}Mg$ | 24.98584 | Moderate |
| $^{26}_{12}Mg$ | 25.98259 | Lowest |
Calculation Basis
The average atomic mass is calculated by considering the mass of each isotope and its percentage of natural abundance.
- $^{24}_{12}Mg$: With a mass of 23.98504 u, it is the most abundant.
- $^{25}_{12}Mg$: With a mass of 24.98584 u, it has a moderate abundance.
- $^{26}_{12}Mg$: With a mass of 25.98259 u, it is the least abundant.
The weighted average of these values, based on their relative natural abundance on Earth, gives us the average atomic mass of magnesium.
Conclusion
The average atomic mass of magnesium is 24.312 u. This value is a weighted average based on the natural abundances of its three isotopes: $^{24}{12}Mg$, $^{25}{12}Mg$, and $^{26}_{12}Mg$.
