Relative Atomic Mass (AQA GCSE Chemistry): Flashcards

1/12th mass of carbon-12 atom

Abundance of each isotope

Weighted average of all isotopes

Ar is average; mass number is one isotope

$\frac{\sum(\text{mass} \times \text{abund})}{\text{total abund}}$

Chlorine-35 and Chlorine-37

75%

25%

35.5

On the periodic table

Different isotopes contribute to weighted average

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

Relative formula mass