Average Mass of Isotopes Calculator

Average Mass Formula:

\[ \text{Average Mass} = \sum (\text{Isotope Mass} \times \text{Fractional Abundance}) \]

Isotope 1 Mass:

amu

Isotope 1 Abundance:

decimal

Isotope 2 Mass:

amu

Isotope 2 Abundance:

decimal

Isotope 3 Mass:

amu

Isotope 3 Abundance:

decimal

Average Atomic Mass:

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1. What is Average Mass of Isotopes?

The average mass of isotopes is the weighted average of the atomic masses 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 average mass formula:

\[ \text{Average Mass} = \sum (\text{Isotope Mass} \times \text{Fractional Abundance}) \]

Where:

Isotope Mass — Mass of each isotope in atomic mass units (amu)
Fractional Abundance — Relative abundance of each isotope (as a decimal between 0 and 1)
Σ — Sum of all (mass × abundance) products

Explanation: The calculator multiplies each isotope's mass by its fractional abundance, then sums all these products to get the weighted average mass.

3. Importance of Average Mass Calculation

Details: The average atomic mass 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 at least one isotope's mass and abundance (required). You can enter up to three isotopes. Abundance values must be between 0 and 1 and should sum to 1 for complete accuracy.

5. Frequently Asked Questions (FAQ)

Q1: Why isn't the average mass a whole number?
A: Most elements have multiple isotopes with different masses. The average is weighted by their natural abundances, resulting in non-integer values.

Q2: What if my abundance values don't sum to 1?
A: The calculator will still work, but for accurate real-world results, abundances should sum to 1 (or 100% if using percentages).

Q3: How many isotopes can I calculate for?
A: This calculator handles up to 3 isotopes, but most elements have 2-5 naturally occurring isotopes.

Q4: Where can I find isotope mass and abundance data?
A: The IUPAC publishes comprehensive isotope data. Many chemistry textbooks and online databases also provide this information.

Q5: Does this work for radioactive isotopes?
A: Yes, but for radioactive isotopes, the abundance may vary depending on the sample and decay over time.