What is iron’s atomic mass? (round to tenths )
The Correct Answer and Explanation is:
Correct Answer: The atomic mass of iron is 55.8 atomic mass units (amu).
Explanation:
Iron (chemical symbol Fe) is a metallic element found in group 8 and period 4 of the periodic table. Its atomic number is 26, meaning it has 26 protons in its nucleus. The atomic mass, however, reflects more than just the number of protons—it is the weighted average of all naturally occurring isotopes of iron, measured in atomic mass units (amu).
Iron has several stable isotopes, primarily:
- Iron-54
- Iron-56
- Iron-57
- Iron-58
Among these, Iron-56 is the most abundant, making up nearly 92% of all natural iron. Because atomic mass is an average that considers both the mass and relative abundance of each isotope, the average mass of iron turns out to be 55.845 amu, which rounds to 55.8 amu when rounded to the nearest tenth.
This average mass is calculated using the formula: Atomic Mass=∑(isotope mass×relative abundance)\text{Atomic Mass} = \sum (\text{isotope mass} \times \text{relative abundance})Atomic Mass=∑(isotope mass×relative abundance)
This approach ensures that the atomic mass reflects the mix of isotopes found in nature rather than a single atom’s exact mass.
Atomic mass is essential in chemistry and physics because it helps determine molar mass (the mass of 1 mole of a substance), used in stoichiometry for calculating how much of one chemical will react with another. It also plays a critical role in balancing equations and converting between grams and moles.
In summary, iron’s atomic mass of 55.8 amu (rounded) reflects the real-world, natural mixture of isotopes that make up the iron we find in the Earth’s crust and use in everyday applications like construction, manufacturing, and medicine.