The element rubidium (symbol Rb) contains two isotopes, $^{85} R u$ $"^85Ru$ and $^{87} R u$ $"^87Ru$ , with percentage abundance of 72% and 28% respectively. What is the relative atomic mass ( $A_{r}$ $A_r$ ) of B?

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Answer 1 · 2017-02-05T00:06:40

The relative atomic mass is the weighted average of the individual isotopes.

$A_{rubidium} = 0.72 \times 85 + 0.28 \times 87 = 85.6 \cdot amu$ $A_"rubidium"=0.72xx85+0.28xx87=85.6*"amu"$ .

Note that $R u$ $Ru$ is the symbol of $ruthenium$ $"ruthenium"$ .

The element rubidium (symbol Rb) contains two isotopes, 85Ru"^85Ru and 87Ru"^87Ru, with percentage abundance of 72% and 28% respectively. What is the relative atomic mass (ArA_r) of B?