# Copper has an atomic mass of 63.55 amu and two naturally occurring isotopes with masses 62.94 amu and 64.93 amu. Which mass spectrum is most likely to correspond to a natural occurring sample of copper?

You would observe metal peaks at $63$ and $65$ $\text{amu} \ldots \ldots \ldots \ldots$
""^63Cu and ""^65Cu peaks would be observed.