What is Average Atomic Mass?
The average atomic mass of an element is the weighted average of the masses of all its naturally occurring isotopes. This value takes into account both the mass of each isotope and its relative abundance in nature.
Formula
The formula for calculating average atomic mass is:
$$\text{Average Atomic Mass} = \sum_ (f_{i} \times m_{i})$$
Where:
- fแตข = fractional abundance of each isotope (percentage รท 100)
- mแตข = atomic mass of each isotope in atomic mass units (amu)
- n = number of isotopes
How to Calculate Average Atomic Mass
- Identify all isotopes of the element and their masses
- Determine the percent abundance of each isotope
- Convert percentages to decimals by dividing by 100
- Multiply each isotope's mass by its fractional abundance
- Sum all the products to get the average atomic mass
Example Calculation
Let's calculate the average atomic mass for an element with two isotopes:
Given:
- Isotope 1: Mass = 40 amu, Abundance = 80%
- Isotope 2: Mass = 44 amu, Abundance = 20%
Calculation:
$$\text{Average Atomic Mass} = (0.80 \times 40) + (0.20 \times 44) = 32 + 8.8 = 40.8 \text{ amu}$$
Real-World Application
This calculator is essential for:
- Chemistry students learning about isotopes and atomic structure
- Research scientists working with isotopic analysis
- Nuclear physics applications
- Mass spectrometry data interpretation
Understanding Isotopes
Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This means they have different atomic masses but identical chemical properties. The average atomic mass listed on the periodic table reflects the weighted average of all naturally occurring isotopes of that element.