The average atomic mass of hydrogen is calculated by considering the mass and relative abundance of each of its isotopes.
Understanding Isotopes and Average Atomic Mass
Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons. This difference in neutron count leads to slight variations in their atomic mass. The average atomic mass, therefore, is not simply the mass of a single hydrogen atom, but a weighted average based on how commonly each isotope occurs in nature.
Hydrogen Isotopes
Hydrogen primarily has two naturally occurring isotopes that are significant for determining its average atomic mass:
- Protium (¹H): This is the most common isotope, with a mass of approximately 1 atomic mass unit (u).
- Deuterium (²H): This isotope has one proton and one neutron, resulting in a mass of approximately 2 u.
Calculating the Average Atomic Mass
The average atomic mass is calculated using the following formula:
Average Atomic Mass = (Mass of Isotope 1 × Abundance of Isotope 1) + (Mass of Isotope 2 × Abundance of Isotope 2) + ...Hydrogen Calculation Example
According to the reference provided, the average atomic mass of hydrogen can be calculated as follows:
| Isotope | Mass (u) | Abundance | Calculation |
|---|---|---|---|
| Protium (¹H) | 1 | 99.985% | 1 × 99.985 |
| Deuterium (²H) | 2 | 0.015% | 2 × 0.015 |
| Total: 1.00015 u |
Therefore, applying the formula:
Average Atomic Mass of Hydrogen = (1 99.985) + (2 0.015) / 100 = (99.985 + 0.030) / 100 = 100.015 / 100 = 1.00015 u
Conclusion
The average atomic mass of hydrogen is approximately 1.00015 u, a value derived from the weighted average of its naturally occurring isotopes. This takes into account both the mass of the isotopes and their relative prevalence.
