Periodic Table Atomic Weight Calculator

Atomic Weight

"The weighted average mass of the isotopes of that element."

Atomic Weight Calculation:

Atomic Weight =

[(mass of isotope) (%abundance) ] + [(mass of isotope) (%abundance)] + [….] 100%

Example:

The following example illustrates how atomic weights are calculated based on mass of the isotope and percent abundance.

The two stable isotopes of chlorine have the following masses and percent abundance in nature.

To calculate the atomic weight of chlorine, the mass of each isotope is multiplied by its percentage in nature and then divide by 100.

[(34.9689) (75.77) ] + [(36.9659) (24.23)] 100

= 35.4527 g/mol

The atomic weight of chlorine is 35.4527 g/mol.

Choose an element to calculate the atomic weight:

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