How To Calculate Atomic Mass

Atomic Mass Formula:

\[ \text{Atomic Mass} = \sum (\text{Isotope Mass} \times \% \text{Abundance}) \]

Isotope 1 Mass:

Isotope 1 Abundance:

Isotope 2 Mass:

Isotope 2 Abundance:

Atomic Mass:

Unit Converter ▲

Unit Converter ▼

From:	To:

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 represents the average mass of atoms in a given sample of the element.

2. How To Calculate Atomic Mass?

The atomic mass is calculated using the formula:

\[ \text{Atomic Mass} = \sum (\text{Isotope Mass} \times \% \text{Abundance}) \]

Where:

\( \text{Isotope Mass} \) — Mass of each isotope in atomic mass units (u)
\( \% \text{Abundance} \) — Natural abundance percentage of each isotope
\( \sum \) — Summation of all isotope contributions

Explanation: The formula calculates a weighted average where more abundant isotopes contribute more significantly to the overall atomic mass.

3. Importance Of Atomic Mass Calculation

Details: Atomic mass is crucial for chemical calculations, stoichiometry, determining molecular weights, and understanding chemical reactions. It's fundamental in chemistry, physics, and materials science.

4. Using The Calculator

Tips: Enter the mass and percentage abundance for two isotopes. Ensure abundance percentages are between 0-100% and masses are positive values. The calculator will compute the weighted average atomic mass.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between atomic mass and atomic weight?
A: Atomic mass refers to the mass of a single atom, while atomic weight is the weighted average mass of all naturally occurring isotopes of an element.

Q2: Why is atomic mass not a whole number?
A: Atomic mass is a weighted average of different isotopes with different masses, so it's rarely a whole number.

Q3: How many isotopes can I calculate for?
A: This calculator handles two isotopes, but the formula can be extended to any number of isotopes by summing all (mass × abundance) products.

Q4: What units are used for atomic mass?
A: Atomic mass is typically measured in atomic mass units (u) or daltons (Da), where 1 u = 1.66053906660 × 10⁻²⁷ kg.

Q5: Why do we need percentage abundance in calculations?
A: Percentage abundance indicates how common each isotope is in nature, allowing us to calculate a representative average mass for the element.