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Average Atomic Mass Formula:
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The average atomic mass (AM) is the weighted average of the atomic masses of all naturally occurring isotopes of an element, taking into account their relative abundances. It's the value you see on the periodic table for each element.
The calculator uses the average atomic mass formula:
Where:
Explanation: Each isotope's contribution to the average mass is proportional to its natural abundance.
Details: The average atomic mass is crucial for chemical calculations including stoichiometry, molar mass determinations, and analytical chemistry. It reflects the actual mass distribution of elements in nature.
Tips: Enter the abundance (in percentage) and mass (in atomic mass units) for each isotope. You can add multiple isotopes. The sum of abundances should be 100% for accurate results.
Q1: Why isn't the average atomic mass a whole number?
A: It's a weighted average of different isotopes with different masses, so it typically isn't a whole number.
Q2: How many isotopes should I include?
A: Include all naturally occurring isotopes with significant abundance (>0.1%).
Q3: What if my abundances don't sum to 100%?
A: The calculator will still work, but the result won't reflect real-world conditions. Normalize your abundances to sum to 100% for accurate results.
Q4: What's the difference between mass number and average atomic mass?
A: Mass number is the sum of protons and neutrons in a specific isotope (always a whole number), while average atomic mass is the weighted average of all isotopes.
Q5: Why do we use average atomic mass instead of mass number in calculations?
A: Because elements exist as mixtures of isotopes in nature, so we need to account for all naturally occurring forms in our calculations.