1. What is Atomic Mass?

Atomic mass is the weighted average mass of all naturally occurring isotopes of an element, taking into account their relative abundances. It's expressed in atomic mass units (amu), where 1 amu is defined as 1/12 the mass of a carbon-12 atom.

2. How to Calculate Atomic Mass

The atomic mass is calculated using the formula:

Where:

• Isotope Mass — Mass of each isotope in atomic mass units (amu)
• Fractional Abundance — Natural abundance of each isotope (as a decimal between 0 and 1)
• The sum of all fractional abundances should equal 1 (100%)

3. Understanding Isotopes

Details: Isotopes are atoms of the same element with different numbers of neutrons, resulting in different atomic masses. Most elements have multiple naturally occurring isotopes.

4. Using the Calculator

Tips: Enter the mass and fractional abundance for each isotope. Click "Add Another Isotope" for elements with multiple isotopes. Ensure the sum of all fractional abundances equals 1 (100%).

5. Frequently Asked Questions (FAQ)

Q1: Why is atomic mass not a whole number?
A: Atomic mass is a weighted average of all naturally occurring isotopes, which typically have different masses and abundances.

Q2: What's the difference between mass number and atomic mass?
A: Mass number is the sum of protons and neutrons in a specific isotope (always a whole number), while atomic mass is the weighted average of all isotopes.

Q3: How precise should my isotope mass values be?
A: For accurate results, use isotope masses to at least 4 decimal places as found in standard reference tables.

Q4: What if my abundances don't sum to exactly 1?
A: The calculator will still work, but results may not match published atomic masses. Normalize your abundances to sum to 1 for most accurate results.

Q5: Can I use this for radioactive elements?
A: Yes, but only for stable isotopes. For radioactive elements, abundances may vary depending on sample origin and age.