1. What is Average Atomic Mass?

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

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• Isotope Mass — Mass of each isotope in atomic mass units (amu)
• Fractional Abundance — Natural abundance of each isotope as a decimal (percentage divided by 100)

Explanation: The calculator sums the product of each isotope's mass and its fractional abundance (percentage converted to decimal).

3. Importance of Average Atomic Mass

Details: The average atomic mass is what appears on the periodic table and is used in chemical calculations. It's essential for stoichiometry, molar mass calculations, and understanding elemental properties.

4. Using the Calculator

Tips:

• Enter the number of isotopes (minimum 2)
• For each isotope, enter its mass in amu and natural abundance in percentage
• The sum of all abundances must equal 100%
• Results are shown in atomic mass units (amu)

5. Frequently Asked Questions (FAQ)

Q1: Why is average atomic mass not a whole number?
A: It's a weighted average of different isotopes that have different masses, so it rarely comes out to a whole number.

Q2: How precise should my isotope masses be?
A: For most purposes, 4 decimal places is sufficient. The calculator accepts up to 4 decimal places.

Q3: What if my abundances don't sum to exactly 100%?
A: The calculator requires abundances to sum to 100% within a small tolerance (0.0001%). Natural abundances typically sum to exactly 100%.

Q4: Can I use this for radioactive elements?
A: Only for stable isotopes. For radioactive elements, abundances change over time due to decay.

Q5: Where can I find isotope abundance data?
A: The IUPAC publishes standard atomic weights with isotope abundance data for all elements.