1. What is Weighted Average Atomic Mass?

The weighted average atomic mass is the average mass of all naturally occurring isotopes of an element, taking into account their relative abundances. This value is what appears on the periodic table for each element.

2. How Does the Calculator Work?

The calculator uses the weighted average formula:

Where:

• \( \text{Avg} \) — Weighted average atomic mass (amu)
• \( \text{abundance} \) — Natural abundance of each isotope (%)
• \( \text{isotope} \) — Mass of each isotope (amu)

Explanation: The formula accounts for both the mass of each isotope and how common it is in nature.

3. Importance of Weighted Average Atomic Mass

Details: This value is crucial for chemical calculations, stoichiometry, and understanding element properties. It explains why atomic weights on the periodic table aren't whole numbers.

4. Using the Calculator

Tips: Enter isotope masses in atomic mass units (amu) and abundances as percentages. The sum of abundances should not exceed 100%.

5. Frequently Asked Questions (FAQ)

Q1: Why don't we use simple average of isotope masses?
A: A simple average would give equal weight to all isotopes, while in reality some isotopes are much more common than others.

Q2: What if an element has more than two isotopes?
A: The same formula applies - just include all isotopes and their abundances (summing to 100%).

Q3: Why are atomic weights not whole numbers?
A: Most elements have multiple isotopes with different masses, so the weighted average is typically not a whole number.

Q4: Where can I find isotope abundance data?
A: The IUPAC publishes standard atomic weights with isotope abundance data for all elements.

Q5: Does this apply to radioactive elements?
A: For radioactive elements with no stable isotopes, the mass of the longest-lived isotope is typically used.