1. What is Weighted Average Atomic Mass?

The weighted average atomic mass is the average mass of all naturally occurring isotopes of an element, weighted by their natural abundances. It accounts for the fact that elements exist as mixtures of isotopes with different masses.

2. How Does the Calculator Work?

The calculator uses the weighted average formula:

Where:

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

Explanation: The calculator sums the products of each isotope's mass and its abundance, then divides by 100 to get the weighted average.

3. Importance of Atomic Mass Calculation

Details: Accurate atomic mass values are essential for chemical calculations, stoichiometry, and understanding element properties. The periodic table displays weighted average atomic masses.

4. Using the Calculator

Tips: Enter at least one isotope mass and its abundance. You can enter up to three isotopes. Abundance values should be in percentage (0-100%).

5. Frequently Asked Questions (FAQ)

Q1: Why is atomic mass not a whole number?
A: Atomic masses are weighted averages of all naturally occurring isotopes, which have different masses due to varying numbers of neutrons.

Q2: How many isotopes should I enter?
A: For most accurate results, enter all known isotopes. For elements with only one stable isotope, just enter that one.

Q3: What if my abundance values don't sum to 100%?
A: The calculator normalizes the calculation based on the total abundance entered, but for most accurate results, use complete isotope data.

Q4: Why are atomic masses measured in amu?
A: Atomic mass units (amu) are convenient for expressing the masses of atoms, where 1 amu is defined as 1/12 the mass of a carbon-12 atom.

Q5: Where can I find isotope abundance data?
A: Reliable sources include the IUPAC Technical Reports, NIST Atomic Weights and Isotopic Compositions, and nuclear data tables.