1. What is Average Atomic Mass?

The average atomic mass is the weighted average of all naturally occurring isotopes of an element. It accounts for both the mass and relative abundance of each isotope.

2. How to Calculate Average Atomic Mass

The formula for average atomic mass is:

Where:

• abundance — Natural abundance of the isotope (percentage)
• isotope mass — Mass of the isotope in atomic mass units (amu)

Explanation: Multiply each isotope's mass by its natural abundance (as a percentage), sum these products, then divide by 100.

3. Importance of Average Atomic Mass

Details: The average atomic mass is the value shown on the periodic table for each element. It's essential for chemical calculations and understanding elemental properties.

4. Using the Calculator

Tips: Enter the mass and natural abundance for each isotope. Ensure the abundance percentages sum to exactly 100%. Masses should be in atomic mass units (amu).

5. Frequently Asked Questions (FAQ)

Q1: Why don't the abundance percentages always add up to exactly 100%?
A: In nature, some elements have very rare isotopes that might not be accounted for in simple calculations. For our calculator, the sum must be exactly 100%.

Q2: How many isotopes can I calculate for?
A: This calculator handles two isotopes. For elements with more isotopes, you would need to extend the calculation to include all significant isotopes.

Q3: Why is the average atomic mass not exactly the mass of the most common isotope?
A: It's a weighted average that accounts for all naturally occurring isotopes, not just the most abundant one.

Q4: How precise should my isotope masses be?
A: For most purposes, 4 decimal places (e.g., 34.9689 amu) is sufficient, though more precise values are available in scientific literature.

Q5: Can I use this for radioactive elements?
A: For radioactive elements with very short half-lives, the natural abundances may vary, and special considerations apply.