Final answer:
The relative atomic mass of copper (Cu) is not a whole number because copper has two stable isotopes: copper-63 (63Cu) and copper-65 (65Cu). The atomic mass of copper is the weighted average of the masses of these two isotopes, taking into account their natural abundances.
Step-by-step explanation:
The relative atomic mass of copper (Cu) is not a whole number because copper has two stable isotopes: copper-63 (63Cu) and copper-65 (65Cu). The atomic mass of copper is the weighted average of the masses of these two isotopes, taking into account their natural abundances.
The atomic mass of 63Cu is 62.929595 g/mol, and its abundance is 69.09%. The atomic mass of 65Cu is 64.927786 g/mol, and its abundance is 30.91%. Using these values, we can calculate the atomic mass of copper.
The formula to calculate the relative atomic mass of an element is:
(Atomic mass of 63Cu * Abundance of 63Cu) + (Atomic mass of 65Cu * Abundance of 65Cu)
Therefore, the relative atomic mass of copper is:
(62.929595 * 0.6909) + (64.927786 * 0.3091) = 63.55 g/mol