Question

An element has three naturally occurring isotopes with the following masses and percentabundances:Isotope 1 = 183.6 amu with 75.20% abundanceIsotope 2 = 186.9 amu with 10.10% abundanceIsotope 3 = 193.5 amu with 14.70% abundanceWhat is this element's average atomic mass?

Answer 1

The average atomic mass is 185.4 amu.

To calculate the average atomic mass of an atom from its isotopes, it is necessary to multiply the mass by the percentage of each isotope, then sum them all, and finally, divide it by 100:

`\begin{gathered} \text{Average atomic mass=}((183.6\cdot75.20)+(186.9\cdot10.10)+(193.5\cdot14.70))/(100) \\ \text{Average atomic mass=}(13806.72+1887.69+2844.45)/(100) \\ \text{Average atomic mass=}(18538.86)/(100) \\ \text{Average atomic mass=}185.4 \end{gathered}`

So, the average atomic mass of that element is 185.4 amu.