Chemistry · Chapter 2

Isotope Mixer

The mass printed on the periodic table is a weighted average of the isotopes. Slide the abundances and watch that average slide too.

The mix and the average bar height is abundance

Isotope abundance and the weighted average mass

The marker on the line is the balance point of the bars. Raise the heavy isotope and the marker slides right. The average can never sit outside the range of the isotope masses.

Average atomic mass

35.4529u matches the table
Chlorine Two stable isotopes, and the lighter one is the common one.

Pick an element

Set the abundances
What you are doing
Weighting each mass
Each isotope mass is multiplied by its share, then the products are added. A share of 75.76% becomes the fraction 0.7576. The shares always add to 100%, so moving one slider pushes the others.