Isotope Average Atomic Mass Calculator AMU

Average Atomic Mass Formula:

\[ \text{Avg} = \frac{\sum (\text{abundance} \times \text{isotope})}{100} \]

Isotope 1 (amu):

Abundance 1 (%):

Isotope 2 (amu):

Abundance 2 (%):

Isotope 3 (amu):

Abundance 3 (%):

Average Atomic Mass:

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1. What is Average Atomic Mass?

The average atomic mass (or atomic weight) of an element is the weighted average of the atomic masses of its naturally occurring isotopes, taking into account their relative abundances. It's what you see on the periodic table for each element.

2. How Does the Calculator Work?

The calculator uses the average atomic mass formula:

\[ \text{Avg} = \frac{\sum (\text{abundance} \times \text{isotope})}{100} \]

Where:

\( \text{Avg} \) — Average atomic mass in amu
\( \text{abundance} \) — Natural abundance of each isotope (%)
\( \text{isotope} \) — Atomic mass of each isotope (amu)

Explanation: The formula calculates a weighted average where more abundant isotopes contribute more to the final average.

3. Importance of Average Atomic Mass

Details: Average atomic mass is crucial for chemical calculations, stoichiometry, and understanding element properties. It determines molar masses used in chemical reactions.

4. Using the Calculator

Tips: Enter at least one isotope and its abundance. You can enter up to three isotopes. Total abundance must be ≤100%. Atomic masses should be in amu (atomic mass units).

5. Frequently Asked Questions (FAQ)

Q1: Why doesn't the average mass match any single isotope?
A: It's a weighted average of all naturally occurring isotopes, so it typically falls between the masses of the most abundant isotopes.

Q2: What if my abundances don't add up to exactly 100%?
A: The calculator will still work as long as the total is ≤100%. For most elements, natural abundances add up to 100% within measurement precision.

Q3: How precise should my isotope masses be?
A: For most purposes, 4 decimal places is sufficient. High-precision calculations may require more digits.

Q4: Can I use this for radioactive elements?
A: Yes, but only if you're using the stable isotopes' masses and abundances. For radioactive decay calculations, different methods are needed.

Q5: Why is chlorine's atomic mass not a whole number?
A: Chlorine has two major isotopes (Cl-35 and Cl-37) with significant abundances (~75% and ~25% respectively), resulting in an average mass of about 35.45 amu.