Relative Atomic Mass (AQA GCSE Chemistry Combined Science): Flashcards

$\frac{1}{12}$ the mass of a carbon-12 atom

Abundance of each isotope of the element

Weighted average of all isotopes

Mass number is one isotope; Ar is weighted average

Sum of (mass $\times$ abundance) / total abundance

It's a weighted average of different isotopes

On the periodic table

$\text{Moles} = \frac{\text{Mass}}{\text{Ar or Mr}}$

Chlorine-35 and Chlorine-37

75% Cl-35 and 25% Cl-37

35.5

Relative atomic masses (Ar) of elements