Copper has two stable isotopes, copper-63 (⁶³Cu) and copper-65 (⁶⁵Cu). The main difference between these two isotopes is the number of neutrons in their atomic nuclei. ⁶³Cu has 34 neutrons, while ⁶⁵Cu has 36 neutrons. This difference in neutron number affects the overall mass of the isotopes, with ⁶⁵Cu being slightly heavier than ⁶³Cu.

Here is a table summarizing the key differences between the two isotopes:

| Isotope | Number of Protons | Number of Neutrons | Mass Number |

|---|---|---|---|

| ⁶³Cu | 29 | 34 | 63 |

| ⁶⁵Cu | 29 | 36 | 65 |

Despite these differences, both ⁶³Cu and ⁶⁵Cu behave similarly in chemical reactions and have the same chemical properties. They are both commonly used in various applications, such as electrical wiring, plumbing, and jewelry.